Too much AoE

We ran Zul'Farrak last night, again. I think I've been through three or four times now, and I still don't quite know how to play it. It's interesting how different the game play is when you play solo versus when you are playing with a lot of other people - my AoE is a bit too potent until the mobs have been reduced to about half their life, but I'm not really inclined to sit on my hands for half the fight. Clearly I'm missing something, which I'm sure will turn up eventually. The up side, of course, is that I can just ask my guild.