@Taylor, that's not necessarily true. It really depends on what server you are on. My server is always low on tanks and healers and if you are a tank/healer you are pretty much always guaranteed to find a group for anything. So a dual-spec healer-tank pally is golden. Priests are probably the most boring class in the game imo. Shammy's are pretty fun though, I wouldn't mind playing one.
And I totally agree with H2O. Any ranged class is super fast leveling, assuming you can afford potions and drinks for mana is you are a mana user. Grinding is a super slow way of leveling though, you are much better off just questing and stuff.