>>11864391The flail spin is a frame one attack. Its only other use is hitting slightly above you. By simply taking tiny steps and constantly using it, you can spam it to your heart's content and blend enemies into oblivion.
Not worth it against regular dudes, just use normal attacks. cancel them by moving if you really want more dps, but enemies will die in a few hits anyway.
But against bosses, pop the invincibility potion and you'll turn them into shreds, no exceptions.