[Autumn]

I dont think it should give water weakness, thats why river sword exists as it does, to give weapons such as Ensui or water spells some synergy, nor do I think reverse narcus is a good idea, I'd rather see the Ensui's numbers bumped up to GR levels, making it up to 10 flat resistance vs all attacks, that way it does not get out of hand with multi hits.

Kirosh's effect is not that bad, it effectively makes you immune to cheesy cinder/frostbite builds, thats a huge plus in my books, the only downside is its dark damage and dark damage doesn't see much use these days, though I will get into why ignoring elemental resistance on a weapon is not very healthy.

Setsuna is pretty meh and can serve as only a metagaming tool right now, I agree that it needs to be changed but not in the way it can bypass light resistance, a weapon that bypasses resistances is sort of unheard of and not healthy inherently, winter's bite and null shell have some limited uses and they shut down resistances, also so does Divine Judgement (which just got buffed) for that matter.

I'd rather see a different effect for Setsuna all together, perhaps you could change it and all dragon swords to shred 10% elemental resistance to its respective element on hit or something, stacking until it hits 0% elemental resistance, but to flat out nullify resistance? Take narcus for example, why that'd make it better than a razing salamander in the long run of things, and create an unstoppable combo if both were combined.