He'll try and stand with Overeem and the early blitz will wreck him, I dont see Mir having the ability to survive that or fire off a crane kick afterwards.
How the hell does Mir ever get people to the ground anyway, he loves to stand and bang but his striking is so miserable for a guy who's been hitting the pads for 10+ years its ridiculous and his wrestling is non existent.
That said if he does somehow survive the UberBlitz then there's a 99% chance he can pull off a sub or an ugly KO on a gassed Overeem. Honestly I think Reem would be best served dropping some weight so he can work on his cardio. He's basically back where he was a LHW; a terror early on but then he gasses and is easy picking. That 240 range he had early on in Strikeforce was ideal; muscular, strong but still quick and had better cardio. Though his Uberframe did help him with ragdolling Rogers ans stomping his way out of a Brock TD, etc.