Honestly, I'd change AB entirely.
I'd make it do a 30% of MAX HP damage no matter the class, and give it an appropriate cooldown (longer) this would then become the archers "finishing" move to try and kill a low healthed person and would require some skill to using it. As before, every time it came up it was used simply because it did so much damage. I never really found it much of an issue though due to how ridiculously overpowered Tiger neckies are in game.
If it's now working like FlameSword, then it'll need to be lvl 3 before being useful. It'll be pretty garbage until then sadly.