said by Seiton:Based off your post I would suggest playing a Warlock, or Feral Druid. Outside of that I can't think of to many other classes that could provide some difficulty and not be boring.
^ +1. There's something majestic about the affliction rotation. I think that it's not clunky, but takes skill to master. Having all your shadow diseases going off plus shadow bolt spam or a drain life and seeing huge ticks/crits is a very satisfying feeling.
Not to mention that the whole idea behind the Haunt spell infesting your target and then returning their life force to you is just badass.