A Lightning Storm Druid can easily do T100 dungeons with ease and safety. With ease, because it has great damage and aoe. It can do it safely because he can just stay back and can kill mobs in the next screen.
I'm sure other builds can work well, but I've had one of the safest and easiest times with this build. I play HC only, so this is important. Hota barbs can also just bonk away minions and one-shot the boss, too, if you wanted that.