First of all, Spirit is gonna be useless to Warlocks in Cataclysm.
Second of all, Intellect will also be Spell Power, so Gnomes win the Warlock.
Third of all, any Paladin can easily be OP.
But, when the third expansion Cataclysm comes out I'm quite sure the Warlock is gonna be OP with the new SS system.
Type in "Warlocks and Hunters" in YouTube and you'll find the details there, as well as for Hunters.
The best one is Paladin, they're Hybrid, and they wear Plate as Healers, not to mention the Immunity Bubble, which is just annoying to anyone attacking him / her.
Best ones:
Gnome Warlock.
Tauren Paladin.
Worgen Rogue.
Worgen Hunter.
Goblin Mage.
Goblin Rogue.
Goblin Fury Warrior.
Those are the best types you could get, for Cataclysm as far as I know anyway.
Goblin have 1% Haste, making any quick attacker want it.
Worgen has +15 Skinning, effectively powering Leatherworkers.
Tauren has a powerful Warstomp, which stuns enemies around him, another stun for Paladins.
Gnomes are the best PvP'ers as they have increased Engineering - the best profession for PvP. Also 5% Intellect, a powerful buff which can improve any Spell Damage, which also means Gnome Priest (again, in Cataclysm.).
Dwarven Shaman's are coming too, Troll Druids, Undead Hunters, Human Hunters, Goblins are anything exept Paladin and Druid.
For Worgen it's Paladin and Shaman.
Dwarves are Elemental, realistically speaking, there's Iron Dwarves, Mountain Dwarves, Hill Dwarves, Frostborn, Earthen Dwarves, Rune Dwarves, maybe even more.
Worgen aren't, they're a Savagekin (WoWWiki will explain that) in a way, as they are... possibly derived from Night Elves.
Oh, Night Elf Mages, Dwarf Mages, that's all I can think of so far.
There's a Class Table on the WoW site itself, if you wanna check it out.
- H