frost mages do their dps when they freeze a mob and spam frostbolt + icelance in comination.
Very nice but you need to be tough to watch if the mob is frozen or not and the frost debuff can
break due to other damage on the mob.

So I'd suggest fire. Use scorch at the beginning to get the fire dmg buff on the mob (there is a glyph that it will
stack two times with only one scorch) and then start spamming firebolts and fireblasts. This should give you more
DPS than frostmages.

(correct me if I'm wrong, I've stopped playing my mage when WOTLK was released)

for aoe: dragonbreath and blastwave are very sweet.