I was a backer of Brock for the majority of his MMA career and I say no. He has some very exciting fights, and I think his record is actually pretty good seeing as how all but one of his fights were with guys that were, if not once were, considered top ten heavyweights in the world.
However, even on a business level, the fame and large pay per view draws he had came from his WWE career, not a prior MMA career. In short. If Fedor came out of retirement fought three times in the UFC and went 2-1, he would get my vote to get it. Brock, does not.