I don't play WoW, but I do play mages on EQ. And mages there are pretty decent AoE casters. My tank that I just built up is an SK and SK's in EQ can AoE agro. So, I pull trains with the SK, maintain agro on him, stun with my chanter as often as possible to keep damage to the SK as low as possible and AoE nukes with the mages. Mages in EQ are "glass cannons" as well, but if you can keep agro off them, maybe they can do their DPS unbothered. Some raids I have done in the past with my guild, we had an over abundance of enchanters and clerics and we'd just pull massive trains while all chanters and clerics did AoE stuns and mages and wizards did AoE nukes. Was pretty effective, but you need to be able to keep the mobs stunned through most of the fight otherwise casters go splat. I don't know the game mechanics of WoW, but maybe you guys can do something similar if you have a class that can maintain agro on all the mobs and survive while the AoE nukers nuke....or stuns.