You see, I've come to see any boss that requires 'an arcane series of actions' in order to damage as bad design. A boss should be vulnerable to basic moves, they should just be aggressive enough and with a larger variety of moves and thus a larger variety of tells to learn.
Dark Souls is somewhat like that. You have to deal with the sometimes incredibly long health bars, but most of the difficulty comes from learning tells. Although that doesn't keep it from cheap shots on occasion (Capra Demon anyone?)