Ok lets see:

Warlock: first char to 85, great.
Mage: got to 62, and liking it.

Shaman: this is the class I'm currently focusing on. Unfortunately, I've tried all three specs of this class and found them lacking: Elemental just seems too magey without the fun of moving around, Restoration has too much healing and not enough damage, and Enhancement while having fun dual-wieldiness doesn't have enough mana for heals to keep myself alive since with 680 mana total and the heal costing 233 mana a pop, to heal myself I would be wasting a third of my mana. I got the Shaman to 51, but I don't think this class is the best one for me.

Best move on then, to either the Rogue or the Hunter. Since my Rogue is higher level and has a different playstyle to both Mage and Warlock, I'll go for it first.