Its super probable that this taints work exactly the same that Soulwar taints.
Upgrading your loot/exp in monsters but only giving "bad stats" in bosses.
U have to do this mechanics, but u dont have extra benefit from bosses.
One more time, no one can answer at 100% this kind of questions.
(Soulwar its not confirmed neither, but seems taints doesnt affect at bosses drops)
I hope i helped u,