Sith Assassin takes a lot of skill to be good and keybinds is a must for this class. At lvl 44 you should have tons of abilities to burn 1-2 targets down fast. I suggest you read up on talents and skills and use them appropriately.
I am lvl 42 at the moment I top almost every warzone in dmg meters and kills. Once again class takes a lot of skill to be good with, not like sniper or trooper.