The Death's Rush Passive is an awesome idea for the passive of the ankou weapons, however it's extremely held back by the fact it only works on rolling the chance after YOU kill a mob, meaning the passive is worthless inside dungeons and not great while leveling either especially since it only last for 2 seconds.
The easiest way I see to fix this passive to make it usable is to have it work on hit much like waterbomb. Every time a mob is hit it rolls the chance for death's rush, or you could just have it "per cast" like arcane insight on the 150 and 175 elementor sets if you're worried about it getting out of control for AOE.
Right now the Cursed weapons mainly server the purpose of a bloody weapon upgrade, but with no real passive and no life steal either it can be harder to make it work to get the increased damage of the weapons, changing the way the passive procs would make it much more appealing to use over bloody gear and a good step up for AoErs who can't afford the coral weapons.