Tell that to progression at first the adds weren't dying hence need to split a dps to kill them, also in dream phases like ToES scene you get a lot of aggro with the AE (but then least you can cast while moving). Dark Shamans we 3 man tank so don't have any issues and fall asleep during it.
Better example then HC Immersius.
Point still stands however that AE in itself is harmful to the mage and the raid.