Pretty sure that even with the poison changes, 51/18/2 is superior to 51/13/7, though by less than before. Work on your expertise. I understand that it isn't the end all with mutilate anymore, but it is still a viable stat to try and cap, though replacing all your gems for expertise is a bad idea. Maybe shoot for
http://www.wowhead.com/?item=50001 but then your hit would be far above the cap....its a tough situation.
Your nightmare's tear is in a terrible spot...put it in your helm, and put two Stark Ametrine's in your boots. Or just Quick King's Amber if you are into that, but I lean towards Starks.
Do you find that you ever use rupture? If you do, you are doing it wrong, unless it is a 1cp one to kick off HfB. My personal choice is to lose Blood Spatter and take Fleet Footed. Then remove your Rupture glyph and take Tricks of the Trade to boost raid dps.
Change a few gems, change your spec, reglyph that one glyph and you should be set. Overall, not terrible, but spreadsheet sometime to maximize your gemming/speccing.
Do not rate me...find someone who got skipped over and do them.