12 hours to 60 means he almost certainly just grinded it by leeching quest rewards. Also lol @ dying with Diamond Skin available. I'm guessing he had a terrible spec for soloing as well (do you have *any* plan for dealing with Daltyn's ice orbs?)
Well that's what you get with "power" gamers.
Edit: watching his stream now. He's definitely just leeching his way to 60 through azmodan quest xp. Also he didn't have force-move bound to anything, lol.