Why my rogue not hitting hard cont....?

i have a level 80 rogue thats nearly all epic. my talents are ination and combat 20-51-0 with 455 hit rating. unfortunatley its driving me up the wall that im missing most hits and coming almost bottom on a damage recount when im raiding and doing instances. can anyone tell me why this is as im fed up of having to respec all the time. By the way look for nadenis on world of warcraft armory thats me.