The new dual nikana stance is alright. Once they fix the weird bug that's causing the forced slash on heavy to be offset behind and to the right of your frame, it'll at least have good multipliers (although no guaranteed procs on light attack, sadly.) I feel like a truly good dual nikana would work fine alongside the stance, we're just blinded by how mid Sun & Moon is. And the heavy scythe stance has bad multipliers, but there's a lot of nice slash procs in there. I would call these stances alright. They're not great, but they're not so bad as to doom their whole weapon class.
Assault saws / two-handed nikanas are just bad though. If the Tenet Livia was any other weapon archetype I would never unequip it, but Wise Razor sucks so much that it ruins it. If they ever make another assault saw, they're going to have to pump its base damage way up to account for the terrible multipliers on Butcher's Revelry.
Overall it's been pretty hit or miss, but there have been some hits IMO. I'm done getting excited for new archetypes before I can try them, but I think saying there hasn't been a good stance in five years is a little excessive.