In DS3 stats matter a lot more, so basically any weapon that’s bleed/luck-based. Nothing else can really be as effective as carving off 1/3 of an enemy’s hit points every third to fifth attack.
Other than that it’s Sorceries that give you the highest DPS in spite of being slow (as long as you’re fighting one enemy at a time this generally isn’t an issue - or you can just use the Hidden Body spell and skip everything).
Also, I don’t really see the connection between Demon’s and Dark Souls. Aside from painting with very broad strokes, they’re very different games.