I've found that elemental shamans have some of the lowest dps (given equivalent gear/skill) of any class. My evidence is only anecdotal, but this is based on months of boxing, pugging heroics and raiding (with only 1 toon). I'm not surprised in the least by the OP's dps. I am in the same boat.

I've given up trying to box heroics (other than SFK) and am now pugging heroics with each toon solo to gear each up. I may go back to trying to box heroics after 4.2, if only to try and get Glory of the Cataclysm Hero.