Your letting blind hatred blur your judgement. Look at there fights, Bisping for all the things he does mediocre doesn't get hit often. He moves out well and takes less punches than most against pretty decent competition. Miller is fighter lesser guys and gets hit more. And the wrestling, really Bisping has a fairly decent shot. This is all coming from somebody who is pretty commonly attacked for having and unfair bias against Bisping.
I don't hate Bisping at all. I'm not even biased towards him. He's simply an average fighter. Not particularly good at anything.
Of course Bisping is a "better" kickboxer, he comes from a kickboxing base, but his chin and heart are so poor that it marginalizes his skill.....I mean, Jorge freakin Rivera had him in trouble in his last fight. Miller's defense isn't great, but he has a cast iron chin and incredible heart and is definitely willing to stand and trade.
In wrestling, Bisping isn't much better, if better at all than Miller, especially defensively.
GSP had trouble controlling Mayhem at points in that fight.
And obviously, in grappling, Mayhem has the clear edge, in both credentials, and application.
Even Bisping's usual edge in fitness is marginalized here, Meyhem almost always comes in great shape. I'd still put Bisping a level above, but it wouldn't be by much.