After 3 Beta weekends of testing different builds here is my final product that I have put together.http://www.gw2db.com/skills/calc/thief#3
The build focuses on dealing high amounts of damage over 5-10 seconds while you are in steath.
It is pretty simple concept, it focuses on finding a target (preferably multi targets close together). Activating Devourer Venom and landing 3 Death Blossom's and then vanishing into stealth (with either Hide in Shadows or Blinding Powder and following your target.
Once your bleeds run out (they should be pretty low by this time) jump on them with Ice Drake Venom and beating them down with Heart Seeker and Lotus Strike. During this phase they usually won't last long, although if they do or there is a group don't be afraid to pop your Dagger Storm for some insane damage!
The best initiate i have found by going into the Trickery tree is definitely steal. Most of the time it will give you a slow or more damage when needed (usually used after 3 Death Blossom's).
One of the most important aspects of this build is to never miss a Death Blossom. It is crucial that you pop Devourer Venom or make sure they won't be moving! A lot of people have been hating on thief's because a lot of their moves rely on the target staying still, which can be achieved by either you or a friendly (this is the main reason for the utility skills).
Try not to spam your Death Blossom's heavily in succession as most of the time (with my ping anyway) i will flip around the frozen target although still miss. Make sure you land you first one, and after that land the next two as soon as possible!
Don't try to stay in a group fight too long, unless you are using Dagger Storm in which case please, please, please stay in the fight!
I hope this guide can help the rest of TG who plans on playing Thief!