Hmm. The biggest problem with your character that I can find is that the T9 gear has
way too much ArP. Which isn't your fault at all, it's the fault of the item designers for putting such bad stats on the gear around that level.
If you can, I'd be looking to replace some of your items with Expertise on them with ones who don't so you lose about 4 expertise and don't go over the cap. I'd also be targeting items with haste on them to replace ones with ArPen (http://www.wowhead.com/?item=47043 is perfect and not out of your reach).
I'd also try and get Death's Verdict off Twin Val'kyrs, but I'm sure there's still so many people wanting that so you'll hopefully get lucky and get it. It's a huge upgrade over your Pyrite Infuser.
Also, what kind of rotation are you doing? Open with Garrote (especially if there's no other classes with bleeds in the raid), then Mutilate once, Slice and Dice, Mutilate up to 4 (or 5, but don't Mutilate on 4 to get to 5) combo points, Envenom and then repeat the Mutilate/Envenoms, using a low combo point Rupture when needed to refresh HFB. Use Vanish every time it's off CD and use Cold Blood when you have an Envenom ready (5 point preferably). Your main priority should be keeping SnD up, so if it's about to run out do a low point Envenom.
Fake Edit: I've compiled a
Wowhead profile of what is definitely in your reach and obtainable. It'll probably take a few weeks to get there, but that'll definitely improve your DPS drastically.
Changes:
Nightmare Tear in your bracers (10 str, 10 agi, 10 sta > 20 AP, 15 sta)
Charge of the Demon Lord
Cuirass of Calamitous Fate w/ 20 exp, 40 ap gems
Flamestalker Boots from Ignis 25man w/ Icewalker enchant, this could prove hard to get but he is one of the raid weeklies so you may be able to find a group for him. The boots have great stats and despite their ilvl they're pretty awesome.
Twin Spike
Death's Verdict, lots of people want this so let's just hope you get lucky.
All of those things will bring your stats in line with the caps and hopefully improve your DPS by quite a lot.
EDIT: Yeah, Mutilate is a very boring rotation, one of the easiest in the game (second only to Arcane Mages). Combat has so much freedom it's strange since I originally went Mutilate back in 3.0 to get away from Combat's boring rotation, but now the tables have turned.
For reference, here's my now-defunct Rogue:
http://www.wowhead.com/?profile=us.thaurissan.tyveri Notice how I ignored higher ilvl pieces to stack haste and better stats than ArPen. Now that it's so easy to get T9 and no one runs Naxx etc. it'd be hard to get gear similar to mine, which is a shame. I've never really been a hardcore raider so I rarely ever got BiS gear and just had to make do with what I had, which turned out quite well. I've managed to pull 9k on Koralon 25man, which is sorta why I was harsh earlier.