Ogres already belong to the Horde, they just need better models and a female model. To balance out the Alliance getting another Druid, we could let them be Druids too. Here's my class idea on this:
Alliance - High elves (Druid, Hunter, Mage, Monk, Paladin, Priest, Rogue, Warrior, Death Knight).
Horde - Ogre (Druid, Hunter, Mage, Monk, Priest, Shaman, Warlock, Warrior, Death Knight).