Key is to get your hit points up fast so you can kidney punch after the cheap shot wears off.  Use thistle tea or the talent point (can't remember what it is called offhand - in combat tree) that gives you 100% energy regen (although it has a 5min cooldown). 

For the quick kill must have your slice'n'dice up, even 1 point will should give you long enough to have an effect, and if you put your sprint on at the same time the target won't know where to turn if it does come out of stun lock!

Another good one a lot of rogues forget is to use blind, let your energy build up while you blind the target - you can then vanish and c.shot again if need be, or just KP if you didn't get it off the first time and have enough energy to finish it off.