Bah, it's just the old tradeoff between single-class and multi-class characters: shortterm power, and longterm power. But with the addition of ToB, the 9th level spells, and all the quests that can get you an obscene amount of experience, having a cleric/mage is a very, very good idea. Aerie just may be the most powerful longterm growth character in the game.
Yeah longterm with lots of potions and resurrection investment
