I've been stuck in Act 5 for a few hours now because of this bitch. If you played the demo and are worried that the game is too easy, I can assure you it isn't. The bosses in this game are hard as balls if you don't use any charms and it's mainly because of the new health gauge mechanic that requires you to maintain constant offensive pressure. Basically, if you play too defensively, the boss will just heal itself and the fight takes longer. Imagine if a Souls boss had this kind of mechanic, it would drive you nuts too.