Not entirely sure if this is a bug, but my finisher effect is not working

This only happened recently, so I'm not sure if it's due to an option I selected or if it's potentially a bug.

Currently in act 2, Spires of Deshar. I have the purifier's swordstorm rare finisher effect equipped. To my understanding, rare monsters are mobs that spawn with yellow names. Please correct me if I was wrong, but I do noticed my player character saying a one-liner whenever he kills one of those.

I've seen the finisher effect activate multiple times during Act 1, but noticed it not being there in Act 2. I've tried resetting both game and interface settings to default, as well as reclaim and re-equip the effect as well.

Been testing it on all rare monsters i've encountered and still nothing. Am I maybe doing something wrong, or is this possible a new visual glitch or something?