I think it's just a stat debuff actually, unfortunately. I would have preferred it if the movesets were also altered, but I imagine that would have been too hard to properly implement. Instead, it's just number tweaks - less damage dealt by the enemy, you deal more damage. That was fine for me, though, because I still got to experience the entire fight without any compromises but I didn't get two-shot by basically any enemy (NG++ in the DLC, before NG+ runs in the DLC have been nerfed a little).