I think that Mirko is the exact same man/fighter that he was over a year ago when he KO'ed Wanderlei Silva. The problem is that his style doesn't fit well with the UFC and its fighters. Over in PRIDE, Mirko had the ring to work with, he would be able to bully his opponents around then back them into a corner where they would have no where to go, then knock them the F'k out - while in the octagon he had trouble catching them since they would be able to just continuously circle around the octagon and Mirko would have no place to back them up and trap them, his debut fight vs. Eddie Sanchez is a perfect example of this. The other problem is the fighters in the UFC, simply put they strategize and analyze a fighters strengths and exploit their weakness before fighting them (his fights with Cheick Kongo and more noticeably Gabriel Gonzaga are examples of this) and I noticed that in PRIDE they didn't do that nearly as much, they'd just go out there and brawl. This worked well for Mirko because some fighters that may have beaten him with a well thought out strategy when they lost. This is also one of the main reasons as to why Fedor Emelianenko was so successful in PRIDE, since he would strategize before a fight while his opponents didn't.
Mirko will be back in old form when he fights at DREAM.