So I'm on NG+.. 1.11 / latest patch
I've got all the cards, compared everything to lists online successfully and yet the quest won't go away. Are the hearts of stone cards mandatory now for it or what?

The HoS cards are definitely NOT mandatory in non-NG+, so I would think they aren't mandatory in NG+ either. I just got the achievement the other day in a regular game before I began HoS (though I did have HoS installed). I haven't tried NG+ yet but it seems like a lot of bugs are tied specifically to that game mode.