Mir wilts under pressure, especially while being mauled in the clinch against the fence, which is Overeem's MO. He doesn't have Travis Browne's courage under fire, and would not come back from a similar assault. He struggles to get fights to ground, has been both ragdolled and bullied to a losing decision and brutally finished in the past few years, showing that is beatable in a number of ways. On paper this is a horrendous matchup for Mir.
So why do I have this weird feeling that Mir will submit him in the first?
I would say AO also has a tendency to wilt while under pressure. And Mir has come back from having the crap pounded out of him, look at Brock I and Nog II. But that was a few KOs ago.