A little frustrated with my dpsFollow

This is Casper from farstriders and I am looking for some helpfull advice on my dps..

This is my armory http://www.wowarmory.com/character-sheet.xml?r=Farstriders&n=Casper

My chest I still need to enchant with plus 10 stats. My guildy is almost able to do it!

I am running the pinnacle to get Sovereign's Belt 705 Armor +51 Agility +67 Stamina +33 Intellect Equip: Improves hit rating by 43. Equip: Increases attack power by 132.

With my flask and buffs my attack power is usually around 4000 and crit around 25%
hit rating is 251. My shot rotation is steady shot, auto shot and I keep serpent sting
on the target as well as hunters mark!

Now when I attack the stormwind dummies I get around 2,900 dps but in herioc instances it seems the most
I can ever achieve is 2200 and average 2000 dps. I keep improving my gear with epics but my dps seems to stay the same. I figure there must be something I am overlooking!

I must admit I am only just learning to play my character well. Untill recently I thought armor was important to me to help me survive. I have done a lot of research and had help from new friends. I now concentrate on attack power, crit and hit.. I am wondering tho If my main concern should be agility?

If anyone can see any improvements I can make that will help me move my dps up it would be greatly appreciated!

Thanks in advance and Happy New Year to everyone!
Casper