Kill order for me is:

Fire Mage
Frost Mage/ Ele Shaman
Hunter
Ret Paly / Warrior / Enhancement Shaman
Priest / Non Cheat Death Rogue
Warlock / Cheat Death Rogue
Paladin / Resto Shaman / Druid

Basically take out what the largest threat to you is in terms of damage, and go from there.