I like what you started with. But I think a lot of your gear can move around. Maybe try getting a better MH to start. I think you can find a lot more DPS coming from a better MH, soemthing with a +int roll, CD, and open socket. YOu can simply swap it with an EF, and you will notice a huge gain.
I like that you didn't go the legendary route with your gear, but some solid rares.
With your spec, I wonder if you need the lifesteal from the dogs, or if it is just comfort. You have a good LOH on your weapon, and I am not sure that you need it from the dogs. If you dont, try switching out the dogs to garg, I find him to be a better tank for elite fights. Or if you want to keep the dogs, maybe try sacrifice? Also, spirit Vessel, not sure how much you actually die, or how much you use this, but maybe try something else. If it isn't triggering all the time, you might get more use out of something different.
I would just experiment with him more. Seems like a lot of your spec is filling gaps in your gear (mana regen rune on spirit walk, spirit vessel, etc...). If you upgrade some of that into your gear, you might be able to change your spec to pump out more dps.