I totally disagree with this statement. I think that when VK went for the super KO, he was at risk of hyper-extending his arm, so he decided to lighten up his punches a little. He learned how not to injure himself after the Byrd fight. He's got one of the best KO ratios of all time. Your statement actually sounds quite stupid.
Corrie was one of the greatest frontrunners the division has ever seen. He could've done more had he been fully dedicated, but even then, it's unfair to call him a disappointment in the grand scheme of things.