Over at the weapons feedback section you have a plethora of threads on this matter, you can chime in there. But since you already posted it here... that's if you shoot properly. I even had one time where I shot a normal armored person 4 times because I wasn't aiming properly. It's just the situation your in. In the time those 2/3 shots would have been fired, I could've emptied an entire clip of prowler in that person and he could've died 2 times over.
It's all relative basically.