Well, I manged to make it to Cruel difficulty on my hardcore character. Actually just beat Brutus the warden. So far no major problems.
If not for lag spikes the game is pretty easy with a few skills. Here is what I have going.
I am playing a Shadow. I use a dagger for now, but have used swords, foils, and even a mace as the dps of it at the time of the find was much higher than anything else I had found.
I am currently building evasion and energy shield as my main 2 defensive stats and I use a shield. I am built and itemized to still have capped 75% elemental resist rates even when I entered Cruel difficulty.
Basically this is my "safe" playstyle.
I see a new area or room. If I see the monsters before they agro I toss out a fire trap and then a decoy totem from behind them. As they run up to the totem, they get hit by the trap, and I just retrap and toss out more totems. Any of them get frisky I have lightning strike. Some of the monsters are range and a bit more of a handle to deal with. For those I use whirling blades to get on top of them fast, smack that one pesky mob (like a necro summoner), and whirling blades away to safety. I have found that if you run a circle strafing pattern around monsters they can't hit you if you have 12% or higher run speed. With 18% run speed currently, I rarely ever get hit when strafing.
So it's a matter of tossing traps, totems, and circle strafing. On bosses that tear down my totem in 1 hit and are hard to go toe-to-toe with, I use viper strike. Totem at range to get the boss going to the totem, run in and hit with 1 or 2 viper strikes, then whirling blades away before the boss kills the totem and smacks me.
The only "Oh shit!" moments I have currently are lag spikes and chaos damage. I don't have much health right now in Cruel sitting at 400ish health. I have far more Energy Shield than health. I was planning on going with a CI build overall so this works well enough. But every time I get hit with chaos damage it has been OH SHIT! and hitting my health pot while running in hopes the health pot keeps up with the chaos damage drain. So far it has. Until I get ready to pick up CI though, I'll grab the 2 chaos resistance nodes that I'll spec out of later along with some chaos resistance gear.
But for now, even those oh shit chaos damage moments are rare. With my current tactics I hard ever get attacked in the first place much, and when I do I rarely get hit with my high evasion and high block chance off my shield. I only wish Phase Acrobatics wasn't after Acrobatics as a keystone. I don't mind losing the armor value, but losing my energy shield would kill me.
So I'll probably get to a point where I can farm Cruel for the gear and levels I need for having all the skills needed before assigning that one point eventually into Chaos Innoculation. Then I'll happily dump all my chaos resistance gear, passive points, and health nodes points I've picked up. With high evasion, high energy shield, passive support for energy shield, a high chance blocking shield, and energy shielding leeching I should be sitting pretty. Assuming a lag spike or inattention to chaos damage doesn't kill me.