There's nothing wrong with leveling as deception. I leveled as deception at launch all the way from 1 - 50 with no conflicts whatsoever. I didn't touch talos though, I used khemmy val val.
methinks the problem lies between the computer and the chair.
btw, if you're looking for a stealthy, ninja-like character (ya know, an "assassin" lewls) you've chosen the wrong class. Yes the name of the class is assassin, but every significant action takes place outside of stealth. I would be quick to liken it to a sort of melee wizard(like an enh shaman in wow) more than anything.
Also, there's nothing deceptive in deception. The names given to the class and it's abilities aren't appropriate it seems