I enjoy cherrypicking wind golems out of the storm ogres, It's like fishing. I have no idea why I enjoy it so much but I do. It's challenging.
Easiest mobs, smacks too much of the old 'what do you hunt and why' nerf... pass.
Hardest mob for me is Mhedon; I do crap damage as a Ranger (preach on, Gopher... amen), I can't stun him, and he hits a ton. if I time his attacks right, I'm fine. if he suprises me, I'm sucking sand. Most annoyingly hard mob are WA oracles. I simply do not have enough burst damage to get them down effectively.