Fire can theoretically do reallllly great dps even in aoe zerg fests but your threat level will probably hold you back from walking up to a pack of mobs and doing a Dragon's Breath, insta flamestrike, blast wave, insta flame strike. It's difficult to maximize fire aoe damage for a variety of reasons but if you want to try then....
use this
spec. You get the added hit from Precision and lose a bunch of your sucky talents in favor of raw power increases. Also your glyphs are weak. Fireball, Molten Armor, and Living bomb are the way to go. The minor glyph of blast wave is also a good pick up. It's fairly annoying for tanks when you knock back mobs and sucky for you when you throw some of them out of range of flame strike.
The cookie cutter Arcane 57/3/11 build is really easy to play in almost any situation and would be a good way to go.
Frost is easy to play as well. Load up on offensive talents that increase damage/crit and spam blizzard until there are fewer than three mobs left, then frost bolt/ice lance as needed while keeping your elemental out for as much kill time as possible.