I think there's some confusion--at least on my part--on the assassination ability, specifically how it relates to thief backstabbery. For one thing, the last sentence in the ability write-up, "The target must be completely unaware of danger and not otherwise engaged in combat; in effect, this is a snipe attack"--this refers only to the use of missile weapons, right? Not to the ability in general.
So, to be clear, the assassinate ability encompasses and goes beyond backstab. Is the process envisioned something like this in combat:
1. Assassin character maneuvers into position however s/he chooses (hide, move silent, invis., whatever)
2. On attacking, check for surprise
3. IFF surprise is achieved, roll to hit at +4
4. IFF hit, check against assassination attempt table
5. IFF assassination attempt fails, roll damage per backstab level
Right? Or can assassination attempts in general not be made in combat? Does that mean the assassin can try to backstab without trying to assassinate?