I don't know how widespread this issue is, but I first learned of this type of bug from this video:
https://youtu.be/KQOfQboyimw
And that made me realize something I've known for months may have actually been a bug this whole time: the Carnis set bonus does not trigger off of heavy attack-inflicted DOT proc kills, even though the weapon it's "meant for" the Quassus, is made for heavy attack DOT (slash) proc kills; and further testing with Nepheri with nothing but Spinning Needle and Ca