I would tend to disagree just a little bit with you. I do understand that at close range it IS a one-hit-kill, but the range at which that happens is usually just outside melee range or a little bit closer in even. I think it is a skill-based thing. It works well with Promethean Vision, and it's often just a timing thing. If you could hold the charge for as long as you wanted, THEN I would absolutely agree that it would be overpowered, but the fact that it takes half of a clip, has a charge time, and discharges pretty much as soon as you reach full charge still leads me to believe that it's not overpowered, at least not yet.