His chin isn't the problem. His poor defense and boxing is the issue. His size, length and body kicks alone make is standup tough to beat. He should have learned basic boxing fundamentals like a real jab that he brought straight back to keep his defense sound. He pushes his jab and lets it drop which leaves him open to counters. Bisping flatout told him this, but Luke is too arrogant to see his own faults and weaknesses. DC is much shorter, but outboxes many opponents because he learned proper boxing. Luke refuses to do so, and will continue to get whacked out making the highlight reels for opponents. Branch damn near did it too. His only chance is to turn pure grappler and try to avoid striking anymore. The blueprint is now out for how to beat him striking.