Best Caster class for WoW?

I'd ask the forums, but I just felt like putting it one here. Now, I have an 85 DK, and I have a 67 Pally that I'm leveling, and I've been thinking, what do I want next? I reaalllllyyyy like the pally mechanics and such, and I was told Shaman was kindasortamaybe close to that, but I've heard they suck in PvP, and that's what I base my favors on. So, suggestions, and please back them up. :D Thank you much.