My advice: play Assass. Sub is often higher in theoretical DPS than real DPS, you will do better with a spec you like.
I've been playing Assass this whole time and have yet to be beaten by any other spec.
Indeed, don't follow the sims blindly.. Try out the different specs and see for your self what you manage to pull more with.
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I am however still waiting for any dagger to drop.. been clearing Normal since first week, and 6/7HC for 3 weeks and still havent see one dagger drop (We are ranging from 12-13 to 18-20 players in our raid group). So sick and tired of combat, though it was nice luck to get the HC fist weapon and normal axe the first day :P