I just beat him now too. I lost when I tried once during early access. I lost again at release. 3rd time was the charm. I think it is because the last update took away one of its bonus willpower points so it couldn’t do quite as much each turn (depending on its cards). Played on medium and didn’t lose any heroes this time, but I was close to losing one. I dumped a bunch of defense on him and got him out of the way in time.