The One and Only Poldaran wrote:
As easy as it is to level with all classes, it simply boils down to: Whichever class most fits your playstyle will absolutely be easy leveling.
So pick whatever sounds fun to you.
Edited, Dec 1st 2011 5:45am by Poldaran
To elaborate on that a little, almost every class gets some sort of self-healing mechanic pretty early on. I think hunters are actually the only class that doesn't have good self-healing, but they also have a pet tank from level 1. Mages can glyph Evocate, Warlocks have there purple swirly spell that gives back health and soul shards, Rogues have Recuperate, Warriors have Victory Rush, and DKs have Death Strike. Then you have the 4 healer-hybrids, who obviously have healing spells.