Goblins have some really buggy scaling that affects players but not (all?) minions. If you go back to normal mode and try to kill a goblin then it will still take you several hit, but the moment your follower hits it, it dies instantly. I don't know if that's what happened in the video but it sure seems like the buggy scaling had something to do with it.
Getting a Maximus for my follower as we speak. xD
Awesome video
+1