TC, if you are going to use something...use aero, not blizzard II... aero is 200 potency single target, blizzard II is 50 potency aoe, so you at least need 4 mobs so that aero = blizzard II. Not even accounting that aero costs less mana, is instant cast and isn't melee range.

You can do however what people have suggested. Cast protect on your party and quickly switch your cross class spells.

Mobs hit hard in brayflox NM btw xD.