Actually Brock Lesnar would be more like the UFC's version of former 8 time UFC Winner Dan "The Beast" Severn. At the time Dan was in the UFC he took a whole 5 days to learn the training involved. He caught on quick making UFC history, and he was an AWA wrestler. Back in the pre corporate days of wrestling.
Brock is like the "The Beast" except with tattoos. The only difference is he is not as polished as Severn was. The reason he got a title shot early is because the heavyweight division was really thin, and it was perfect timing for him to even it out. Also if you're not big, agile, and strong as an ox you shouldn't be in the heavyweight division, so you can't really dislike Brock for having those natural abilities.
Brocks downfall will be his inexperience against a Frank Mir whose looking like a solid, and fluid fighter as far his strikes, and submissions go.
Brock is a striker, and a good one. He punches like a sledgehammer. The first fight Brock just rushed the fight, and Mir caught him a little too easily. Mir is a submission specialist, he'll have to rely more on Brock taking him down, and then working from the guard to catch Brock again.
I am calling for Mir to be the Undisputed Heavyweight Champion in the 3rd round. I think Brock has improved a lot since the first fight, but I think he needs five or six more fights before he gets another shot at the belt.
This is of course after Mir wipes the floor with him whenever the title fight is announced.