Well, the first issue I see is that your weapon is HORRIBLE. Run the Arena of Annihilation scenario and you'll be better off. Secondly, you're not hit or Expertise capped for heroics, so that could contribute to the issue a great deal.
But, the biggest thing imo, is how comfortable you are with your spec. I was doing 30-35k DPS around your gear level as BM, which is a spec I HATE with a burning passion, so I switched to SV, my personal favorite spec I had mastered over the course of cata, and jumped to 35-40k sustained. Now I can burst upwards of 100k DPS and, depeding on the fight, I can sustain from... 53-65k And, before you call BS, it does depend on the fight. Single target fights that require no movement are the ones I end in the 55-60k range, though movement fights are slightly more taxing.
So, like I said, play what you're comfortable with. I've seen people say all hunter specs are garbage atm, but rather close in terms of DPS, so do what you enjoy. But, if I remember right, BM was Simulating at 4-6k DPS higher than SV at full HT14 gear and MM was 4-6k behind SV.