I do prefer the trinity system, but some games out there destroyed it when they had it (example: TERA).
There's some advantages and disadvantages to both, which - in my opinion - can be:
PROS
º Roles are obviously specialized, well-defined (when done right). You prefer DPS? Go for it, no mistakes possible. Roll that Berserker or that Warrior and stay away from the Priest (just the name I use for a typical dedicated healer class).
º Fights are - generally speaking (when done right by everyone in the party, or raid) - more organized, less chaotic (
when done right). If the tank holds aggro and the game relies on "back crits" (such as TERA) for DPS, then other than having to move around for map / boss / attack mechanics everyone is constantly positioned behind the boss instead, while the boss constantly attacks the tank (again, when done right, AND when that system is still in the developers' own mind). It makes the fights more stable, easier to memorize and simply more organized. So the boss won't run around like a headless chicken attacking everyone equally because there would otherwise be no trinity system, hence less "chaotic" fights (then again as mentioned, not all games that do have a trinity system actually respect that very system after some point in their life span, such as it is the case with TERA; a game that completely lost track of it at this point and makes it 90% useless / irrelevant).
º Some MMO players, believe it or not, have
always been playing
one type of roles in their entire MMO "career" (and usually specifically looked to play MMOs that allowed to select a specific role, of course). I've known a few guildmates over the years (across a few MMOs) whom
never touched the 'tank', or the 'healer'. And if they did (a few told me) they just could not feasibly "get it", get in touch with the role, to play it properly (wasn't "natural" to them), it
Just. Wasn't. Working., Period. I do know one person in the main guild I was in (in TERA) who left the game (said he'd "quit") to check out Guild Wars 2. He returned to TERA something like 5 days later, saying that he instead uninstalled it to return to TERA (that was back when TERA itself actually still had its own trinity system still in place and used properly by the devs; that was prior to the Reaper patch for those who are familiar with the game's updates history).
Those 'specialized' players whom are always more familiar / comfortable / natural with one specific role would generally just not feel at home in a game that essentially tells you "
Here, roll this class, and by the way this class doesn't actually mean much because all other classes do the same DPS as you do and will Heal you the same as this class does, as much as it will be comparably 'tankier' with those defensive skills; only big difference is the manner with which you play the game because this class has a Sword and a Shield, but the other ones summons minions instead". In cases like that (such as Guild Wars 2), choosing a "class" obviously just became a question of preferences in game-play style (and perhaps how it was visually portrayed as well), rather than being about actual situational efficiency and usefulness in a party / raid compared to other classes. You prefer the paladin? Fine, you'll just look fancier than the summoner next to you; but the summoner will spawn demons... too bad both of you will neither be better nor worse at this specific boss because this boss doesn't give a rats' ass about your roll, because the devs themselves don't either.
So the 'PROS' of this one point is to say that for players who are used to a specialized role then obviously a trinity system is not only preferred, but sometimes essential because it gives [them] a better sense of purpose and/or direction (as to why you happened to choose 'x' class over 'y' or 'z').
º In a game with a trinity system, and if all is done well from the devs to start with, then most dungeons are
designed to exploit all would-be present classes. Actually, few MMOs managed such a feat (and I can imagine trying to balance dungeons for all classes isn't exactly something easy either; not blaming devs on that one if they can't manage to do that all the time).
Meaning that, of course, everyone present should have a share of their desired
fun, besides the necessity of running said dungeon for gear. If a dungeon has the mechanics to make the DPS sweat for having to be on the move from time to time and not just stand there just mashing buttons, if a dungeon has the boss attack patterns to ask good memorization from the Tank, and if the dungeon has all the damage output on the players from mobs, bosses or traps to ensure that the Healer needs to keep an eye on every players in the party, then there is NO reasons to wish for the absence of said trinity system. Unfortunately, very few MMOs manage their trinity system well enough to a point where you can say that every dungeons available actually do that (in all rooms, in all boss fights, etc).
However, when done right, a well-exploited trinity system makes everyone in the party important. Not JUST the Healer, not JUST the Tank and not JUST the DPS. If the Tank dies, everyone dies. If the Healer dies, everyone dies. If the two or three DPS die, the Tank will too over attrition and/or the Healer will have to keep himself/herself alive because now there's the entire room worth of mobs running at him and the Tank desperately keeps trying on saving the day, making the situation a mess and aggravating the run's run time (to say the least). When something like that happens it's because of GOOD dungeon balance. And, yes, for some people such situations are frustrating, but it goes to show that it is a TEAM effort, showing that the devs did their job at making ALL the roles efficient and that if everyone does what they're supposed to, everything will go well.
º This one might be pushing it a bit (maybe the more casual players wouldn't recognize this as a plus), but I know it's real, since it happened to me (it was brief, but I experienced it). It's the sense of pride, and the knowledge of you being serviceable to others when you happen to be the best Healer / Tank (or DPS) in your guild (not talking about an entire server, but at least in your guild).
It can definitely be gratifying (and a good incentive to keep playing) when you have unanimously positive comments (both in guild chat and live on TeamSpeak for example) when YOU happen to log-in, because everyone knows that you're good at this job, or that you know ALL the dungeon's mechanics, bosses, etc by heart. You're
THE Healer / Tank / DPS that most (if not all) of the guild asks for, to go do that particular dungeon run they need ( "
DUDE you're on! Hey wanna Tank it?! We NEED you there! " / "
OMG OMG, we were waiting for you! Can you heal for us please? " / "
Damn that dungeon has that stupid cyclops boss with that one mechanic that like 1% of the DPS in the server knows how to deal with, and since you're there now you should really come with us! ").
This point, however, can also be / become a negative. If not immediately, it's over time, more on that below...
CONS (they happen to pretty much be counter points to the above)
º With specialized roles, you ALWAYS (100% guaranteed) end up with player(s) who (the list can be long):
1) Don't give a shit about said role, ruining the dungeon run for everyone else (or at least making it much longer than it could be otherwise),
2) Simply suck at their role but somehow refuse to believe it / acknowledge it, or simply don't care at sucking at it and insist on continuing rather than trying another role,
3) You always have that one (or more) guy / gal in your guild that NO ONE ELSE wants to see in their run, but since the person is a really good guy in real life and makes you laugh in TeamSpeak you just can't find the power or will in you to tell him "
OH yeah btw, can you possibly not come with us on that run please? Cause you really, REALLY suck at tanking ".
Bottom line? Some players play the roles that they shouldn't be playing. And some players aren't playing the roles that they should have tried. That. Is. Guaranteed. In. Every. Trinity System-based MMORPG. Ever. There's nothing else to add to this.
º If you happen to be in a starting / baby guild, or at least not a "big" one, you normally don't have more than maybe... say... 10 to 15 players online (at most) which isn't happening every day of the week (sometimes only during week-ends). In such a situation, you RELY on certain players to be online to run dungeons (if you're in a guild, usually it's because you want to avoid 'PUG' runs as much as possible; understandable too). If those players don't show up, then you lack that one Tank, that one Healer, or those two or three geared-up DPSes to run dungeons that day, or that week, or that week-end (or all of it because they might have been online, but you weren't when they were; time zone issues happen too).
Then you're "forced" to run PUGs at which point it becomes a gamble in and of itself. Will you be kicked out of the PUG group you found (or was automatically assigned to by a PUG-finding system if there's one)? Possible, especially if the party / raid leader happens to be elitist and/or simply feels like being a douchebag that day. Sometimes all goes well, fine when it happens. But otherwise, nope, you wander around in town or your "hub" not sure about what to do, you decide to do some dailies maybe, get bored, log out.
When you're not in a guild and happen to be more of a lone wolf type of player and only (or mostly) rely on party finders or just manually searching (or asking for) a party then be prepared to often be ignored (or at least often be inspected for your gear, or asked about your 'experience' because the party leader has the decency to be worried about whether or not you'll screw up those guys' day because you happen to just suck at your role).
º If you happen to be the ONE, good, best Tank, Healer or DPS of your guild, then it can definitely become a chore over time (even if it feels awesome initially). They will RELY on you. If you don't show up, after a while, you'll know about it. It CAN (rarely, but does happen) get to a point where they start acting like your parents. Dude, where were you?! Dude, you're like... 1 hour late for the raid run! Dude, we had a PUG run earlier and it was a mess, you weren't on. Dude, we would uninstall this game if you stopped playing. Dude, can I have your babies? (I'm saying "they", but it's usually limited to maybe just the guild leader or perhaps him/her along with no more than 1 or 2 others, but the gist of it is clear; it can become like a second job and some people DEPEND on you or shit hits the fan).
When that happens, leave your guild for your own health and sanity (believe me, do).
º A trinity system that decays over time because the devs ruin it, makes such a game a complete mess and a disaster. I know some will disagree, but TERA is currently an excellent example. They (devs) come up with new classes that completely and absolutely disregard the threat system and/or don't balance their dungeon(s) with mechanics that make all roles work for it. But mostly they just invent new classes that would have a much better place in a game like Guild Wars 2 or Blade & Soul, or Black Desert, than it would in the very game it was released for.
There is NO point at rolling a Lancer (tank) when you can just roll a Gunner and pretty much face tank everything anyway, not only because the defense you have is more than enough, but also because the final boss of the end-game dungeon you're running Does. Not. Even. Move. and is only 100% purely mechanics-based, actually requiring only DPS and a Healer. And there is no point at gearing up your Brawler (supposed new 'Tank' recently released) with Aggro gear, because your DPS-specific gear combined with your inherent skill's aggro is more than enough to hold it while you just reach as high DPS as an actual DPS class does.
I'm not sure if there's any other cases in other MMOs out there. I for one only know of TERA. But again, when a game actually forget its own system and runs it intro the ground, might as well just uninstall and move to something else (that's what I did).
º Relying on specialized roles can sometimes mean waiting a long time for a raid or a party to fill up, especially during week days (that's often when people are busy with things like... oh... real life, and stuff). Even if you happen to be in a known / populated guild, not everyone is always logged-in. Being "forced" to invite strangers, or you finding a PUG is entirely 100% going to happen sooner rather than later. It is a negative point especially when the game in question is 'dying', its population dwindling by the months (and people in your guild leaving for other interests, other games, or whatever the reasons are).
º Presuming that the developers DO support their trinity system, BUT they happen to NOT know how to balance their dungeons for each roles properly, then you WILL always have that one (or more) particular dungeon that you will HATE Tanking, Healing or DPS'ing in. Not because you "suck in this dungeon", not even because your actual class sucks in that dungeon. No, instead it's because in that one stupid dungeon there's that one specific boss or those two or three mechanics that the developers themselves thought was a good idea to implement, seemingly just to piss you off for some good laughs internally.
CONCLUSION
Without a Trinity system the advantages can be rather obvious, but you of course must happen to like it; obviously it has to be done well by the developers. Sure, the fights can be chaotic or less organized (because everyone does a bit of everything, and no one relies on nobody) but at least if one guy sucks at their "role" (in a game that effectively doesn't have a real role per se) then the entire run is NOT screwed up. Since there's no actual 'tank' and aggro is merely distributed across the whole party and naturally switches around between players (because designed to act as such) then if that one guy dies (whom happened to have aggro) then someone else will "take over" and the fight will just continue while that guy will revive on his own, or reload from the dungeon's entrance. And since there's no dedicated Healer role if people get hurt they just respectively drink their healing pot, or stop attacking to leave combat mode and run in that corner to recover some health by whatever individual means they have.
Without a trinity system the game can become a question of pure "guns blazing" action without much thought necessary. The only thing that matters is paying attention to the dungeon's mechanics / traps and obviously to learn the boss. But at least you don't ALSO have to worry about 1) doing your "job" (otherwise the run fails or takes way too long), and 2) no one is going to complain about you for not Healing in time, or not holding aggro, or not dodging when you had to as a DPS, etc. No trinity system can be a relief for many, and becomes more of a "free form" game that only asks you to play depending on your preference for a game play style, rather than the
importance of a role. Not to mention that of course without a trinity system parties / raids are formed or found and created MUCH faster (no need to wait for that Tank that doesn't seem to exist when you need one, or two those Healers you need for that raid whom must also happen to be geared up otherwise people will die like flies which dramatically decreases the "pool" of available Healers to choose from).
A game that - in my opinion - does not need a trinity system simply because it happens to have a good non-trinity system design going for it is Blade & Soul. On the other hand, a game that doesn't have a trinity system but would happen to be oh so much better with one is Guild Wars 2. But in the end it's a matter of preferences. I do not "hate" games that don't have trinity systems IF it's done right. And I LOVE games with a trinity system if, also, it's done right.
Ultimately, this is about Black Desert Online. From what I've seen so far, the game Is. Actually. Designed around NOT having a trinity system. For now it does its job well. It's not like there was a trinity system and they'd happen to screw it up at some point. It just was NOT designed with that in mind from the start. In such a case, it's fine (just like Blade & Soul). However, later on when the future PvE updates come out then it MIGHT lean towards the addition of a proper threat system, maybe even one or two new classes to accommodate for more specialized roles, etc. Time will tell. But as of now Black Desert Online is focusing on PvP, and does not need a trinity system. I myself just happen to not be a fan of PvP in most MMOs so I'll avoid it (and it's unfortunate because we don't have many MMOs in NA looking that good and I would have loved to play around that character creation that seems to come out directly from Heaven to make my bad ass Tank).