Since some people have been asking, I don't really have a rotation, more of a series of priorities.

Opening: Ambush (to get enough points to use SnD) > Rupture; starting momentum should et you get SnD without having to open with Garrote. 

Afterwards since Assassin spec refreshes SnD; Keep up Rupture > Envenom at 5 points > Dispatch > Mutilate.

I also use Vanish often so I can fill in combo points faster, or to add a extra bleed, with Shadow Focus, it's almost free dps + points. If I need to vanish for emergencies I use Preparation. A lot of rogues think Vanish is only useful for PvP or aggro dumping, I find it useful for DPS. 

STAB STAB STAB!