Icy-Vein's guide seems more or less accurate. Every guide people have tried to write and post here has been terrible.
Very quick answers:
Stats:
Agi > Hit (7.5%) > Mastery > everything else (fluctuates; use
ShadowCraft)
Rotation:
Use Mut >35%, Dispatch when procced and <35%. Apply SnD once and keep it up with Env. Keep Rupture rolling always. Always Env at 5 CP.
Use you cooldowns on cooldown except the last use of the fight. Save your last use of SB and Vendetta for <35% and line them up together.
Opening:
Don't use Garrote. Ever. You can open with Ambush or Mut and put up SnD or Rupt first. It makes very little difference (
numbers on EJ).
Talents:
SF is the best
Leeching is a very, very slight DPS gain (proc uptime)
ShS is pretty much always best (just 2-3s of uptime beats Prep)
Anticipation is best
Other talents don't matter