Since we are all pre-level 30 and dual spec'd, here is my breakdown of the Mikes Level Dungeoning Toons:
Tanks - Fashionista/warrior, Doppelbock/paladin
Healz - Clerica/priest, Mindgrapes/druid
DPS - Dismike/mage, Flanders/priest, Sybaris/druid, Rollyfingers/warlock
Looks like a nice DPS Elemental Shammy, or healz, would fit right in, yo!
You can check this for a better overview of all our ridiculous alt-based guild!