A lot of WoW mechanics are simply a matter of what target you are DPSing. (ie, Spine of Deathwing) This would be incredibly lame in a game like D3. D3 mechanics are more likely to be either about avoiding major damage, or killing a large pack of adds so that you can get health orbs. By virtue of being an action game, D3 mechanics should be a lot more fast-paced and reaction time dependent. Judging by the one avoidable boss attack in the game right now (SK's teleport strike), boss attacks should be a lot better-paced than in D2 where abilities were either unavoidable (fire nova! hoarfrost!) or so weak you didn't care (mephisto poison cloud!). The teleport strike is balanced to where it is avoidable, but not if you are poorly positioned or slow to react.
Another major difference is that D2 boss abilities had no pattern and gave you little to no warning. Dodging Mephisto's Ice Skulls as a ranged character was pure luck - his casting animation was so fast and unpredictable that you were either already moving or you got hit. On the other hand, the SK has a somewhat (but not completely) predictable pattern of when he will use each of his abilities, which you can see in any of the Level 1 SK kills. This is pretty cool because it allows a skilled player to both predict and react to boss abilities.
It would also be cool if some boss mechanics required players to use the boss's own abilities against them, like tennis ball boss in Dragon Soul. Obviously this would be a much faster-moving ability than the WoW tennis ball.
Edited by PiousFlea, 23 February 2012 - 03:51 AM.