There's no other class that can Heal, DPS, and provide as much utility all rolled up into one package like the Shaman. Paladin is pretty close but not as good for boxing since it's melee DPS. Boomkin is pretty good, and might be as good or better in WotLK... hard to say as nothing is nailed down. Priest is pretty good too but just doesn't have the survivability and utility, or the facemelt burst capability.