I haven't really done any kind of serious testing, but I'm not noticing much of a difference at all when firing it off at 90-100%HP and 40-50%HP. Maybe an increase of about ~10 damage per hit? Again, no real testing, just eyeballing it against the same types of mobs of the same level. It'd be a shame if the coolest looking Gladiator Weaponskill is still as lackluster as before.