Jon Jones's physical traits, skill set and abilities make him more likely to be a champion than Jason Brilz. Thats why their stats and skills in the game should be significantly different with Jones being significantly better.
I cant really discuss the mechanics because Im aware of things that the devs may be doing to address some of the issues you identify. Thats why I said we should just assume that striking will be improved so those issues you identified wont be issues anymore.