Poison Bomb on low level monsters?

The first hit does but the poison can't possibly work like that because it would have a damage range if it did.

You're right, I just tested it and it does in fact take 1/40th of the hp on higher monsters. Maybe it just has a limit as to how low the damage gets depending on character level? Because my lev 88 NW was doing 110 on snails/pigs.