Bayonetta is all about witch time, can't you see? even if you play it on the hardest mode, I doubt there'll be any difference to your fighting tactics. Sure, you'll have to be more careful, and probably really learn a couple of hard-hitting combos, stay back and be more patient, but in the end, where the meat is at is this "evade, +activade witch time+ combo" the enemies won't react any different in witch time just because the difficulty is set on hardest.