Of viable dps specs the lowest ones from my experience are, with BiS DPS numbers from EJ listed if available -
Both shaman dps specs are pretty low. (Enhancement : 12699)
Kitty druids too.
Chicken druids have gotten a lot better since the buff and while I don't think they're rock bottom I do agree that they aren't the absolute tastiest on dps either.
As we move towards BiS gear Ret paladins also fall behind in the numbers game. (13780 with Shadowmourne)
People suggesting rogues/spriests must be on crack. And MM hunters sit at the top to the best of my knowledge with 15,054.