wat skill to add?

i have
MW 0
Assassinate 2
Shadow Shifter 5
Taunt 0
Ninja Ambush 0
Venom Stab 1
Smoke Screen 1
Boomerang Step 30

For you, Assassinate only is only good at lvl20+, since you have maxed Bstep already, so don't add it in, unless you want to Pwn at Papu :+).

But since you seem to be interested in most DPS (dexless DT) in training / grinding scenario's (non-bosses), I would advise you to do this:
- Max Bstep (done)
- Assassinate 1 (Reset if you have the NX)
- Shadow Shifter 1 (Reset if you have the NX)
- Smokescreen 1 (done)
- Max Venom (REALLY adds to DPS in training)
- MW 9 (or 19 if you can afford a MW20 book / get one for free)
- Max Shadow Shifter
- Max Assassinate
- Max Smokescreen
- Max Taunt