It's really just artificial difficulty created by poor players. I can't tell you how many times I've had a lot of trouble or simply wiped because of people not doing something correctly. I recall telling an Enhancement Shaman in Halls of Origination to Purge the big dudes with the flame aura... I never once saw them purged after saying it multiple times. I recall doing Shadowfang Keep and how many healers simply fail at Baron Ashbury. The thing is, that's not even the only fight in the game where the point is to
not heal everyone back to full... although, I can't remember the other one (it's not Anub'arak, although that's similar).
It gets bad enough sometimes that I have to attempt to make up for poor players in ways that I'm not intended to. I usually perform half the interrupts in heroics on my Prot Paladin by saving Avenger's Shield, which is why I can't wait for the Rebuke change to go through!
I actually did Baradin Hold yesterday on my Shaman. I was originally going to go as a tank on my Paladin, but they ended up filling that spot. I was a bit worried that I was going to do some pretty bad damage since I wasn't all that well geared (
armory - I had a green helm on during the raid). I ended up pulling around 11.5k DPS, which I guess was alright for not even being hit or expertise capped. I'd still prefer to do a lot better than that though.