When I have joined a Public Game in Act l, I saw players hitting a boss, so I joined them. Two minutes later I noticed that the boss isn't dying, so I Displayed the Health bars in the Options and I found out that the Boss had Unlimited Health. He got About 5400000+/-2450000000+! Some players like me kept fighting him for about an hour willing it may drop Legendary items..But then we noticed that he recovers his health. That means its Useless! I recorded a Video to show what has happened: http://www.youtube.com/watch?v=jEicPSO9iSk