This post has changed from the original, since finding out new information.
Poison arrows ONLY work on humans.
They should not work on all the other kinds of monsters, including the Templar, Inquisitor, Bishop, Programmer, Loremaster...
It should also not to damage to certain objects... including the Ore and barrels (explosive or not).
The only object the arrow can destroy other than humans are the glass windows...
Vavoom lets you kill practically EVERYTHING with the poison arrows... which should NOT happen.
Fortunately it currently doesn't work on the entity or the spectres.. but that's about it..