I believe they are gone, along with a move away from randomised stat aetherial gear in general.

Do ARR leveling dungeons still drop aetherial gear? I don't do them enough to confirm but I know 5.3 added standardised gear to all of the old dungeons eg Aurum Cuirass, Dzemael Spear, etc.

To those who don't know, Coven weapons was something they tried at the very end of Heavensward, a sort of raid area within Diadem which had a low chance to drop superior weapons.

And I'm sad to see the remnants of those ideas fade away. More people these days seem to be coming around to the idea that it would be nice to have a surprise factor in the game, a rare chance to get epic loot, something out of the ordinary occuring. Nothing is worth anything because we all have the same stuff and nobody stands out.
And yes, raiders using parsers and uploading their parses to external leaderboards didn't like rare weapons having the highest stat potential. Well whatever, there's ultimate now and that has an item level cap/sync, so you still all get to be identical and compete fairly on the external parser game.

So yeah I'd like an alternate branch to the game that incorporates rng loot more and farming for rare things that have some value and consequence. Eureka had some of that, but the rarest items like cassie earrings only boosted you inside Eureka, which is now irrelevant because it was side content for a single expansion and discontinued.