I guess its a matter of opinion.
Do you know when Healing before attack is useless? When at full health.
On the opposite, when it healing after attack useless? When at low health (killing blow).
So, if it heals before attack it will save the person from killing blow, but will overheal when on full hp, while when healing after attack it will heal on full hp, but the person would die from an attack at low hp. (everything between first and last attack doesn't matter, the only difference is first and last hit.)
So if its a bug, its a positive one and I do not understand how it is, quote, "useless".