Corpse destruction and rare finisher MTX

I have Malachai's Demise Rare Finisher Effect equipped, and axe mastery "enemies killed by your hits are destroyed" allocated. As far as I can tell, the finisher never activates.

While I can see how this could be intentional, it's quite disappointing, especially since this finisher and the standard corpse destruction effect are very close in theme and would work great together.

EDIT: I've taken a closer loook, and it seems like the finisher animation begins (there's some swirling blood) but doesn't finish. It's looking more like a bug now.