http://db.vanillagaming.org/?talent#fhxboedAoGcZE00MThis is my current spec and what I've found out to work the best for myself. I've played around with putting 5/5 into Improved Poisons and dispells are just a pain, meanwhile if I put everything into Vile Poisons I just can't get the procs I need, especially when it comes to warriors. This way i get a 24% chance to resist dispell and a 24% chance to apply which feels like the perfect balance in practice. (WTB 3/8 bloodfang or even better, shiv)
Meanwhile Ruthlessness really does not feel worth it as you already have great combo point generation from Seal Fate. The 9% increased damage during Kidney Shot is overlooked, as you can get off 2 Backstabs during a 5 point kidney if you manage your energy properly and if you don't or feel like your target really, really needs to die there's always the option to pop a Thistle Tea, that usually gives me an almost guaranteed 4k damage during a stunlock on anything not wearing high end mail or plate.
The 8 points in Combat should be self explanatory, but in case it's not: Improved Gouge so you can restealth and or regain more energy, Improved Sinister because sometimes you don't have the positioning required to Backstab and unlike mobs a good player will be strafing, facing you though though that does make him vulnerable to Gouge you just need to get that Crippling on, especially since any warrior worth his salt will have Berserker Rage available to him, making Gouge worthless. Improved Backstab, need you really ask?
Master of Deception is a must in PvP I don't know why you elected to skip it... As for my 2 points into Improved Ambush, I used to have those in Elusiveness but it just felt like that never really carried its weight and with so many frost mages out there being able to save Cold Blood for a guaranteed Eviscerate crit is invaluable and less situational than -1:30 CD on Blind and Vanish. (Ambush --> Backstab --> Cold Blood --> Eviscerate has killed any mage i've come across so far, insert Vanish/Sprint/FAP where neccessary).