I wouldn't call that fight outclassing. Overeem wasn't really winning until the knee, even though the fight was less than twenty seconds.
Duffee tried to take his head off, but Overeem remained poised and calm. He countered beautifully. That was definitely outclassed and Duffee pretty much agreed in that interview. That definitely wasn't luck. How many times has he set up his wins with that knee (good night Ireem.) That's his patented move. He has the best pure striking in the HW division bar none. Don't worry JDS is probably next as he's the Brazillian Muay Thai champ. But man I don't think anybody can really deny that Overeem has got some serious skillz. Plus look at the experience factor. He's at his peak right now. "IF" he wins against Werdum then he could take the SF grand prix.