Funny that... Now that all my alts are in 670-690 gear, I was going to do a list of which toons I thought did the job best. Considering all 3 minute cooldowns reset after a boss is defeated, I'd recommend in this order, or something like this.
Feral Druid
Good-great cooldowns, good AoE, great mobility, strong burst.
Frost DK
Good cooldowns, great AoE, decent mobility, strong burst.
Enhancement Shaman
Great cooldowns (Lust every fight), decent AoE, good mobility, strong burst.
Frost Mage
Great cooldowns, good AoE, great mobility, great burst. (Terrible healing).
Ret Paladin
Decent cooldowns, decent AoE, good mobility, good burst.
My Warrior is too far ahead of them to compare, but is, from what I remember, a great soloer at that sort of iLvl. From what I've played, I'd suggest making a feral. Firstly, if you don't like feral, you can always go Balance/Resto/Guaradian at a later date, so that's nice. Most important, though, is that Incarnation is absolutely ridiculous.