Willard was more athletic than he is given credit for, due to the fact most of the footage of him is while he is being battered by dempsey, but for his size he was pretty quick
I really can't see your argument on that one. If he had nothing else, he clearly had exceptional stamina for a man his size.
I disagree with this one. Tubbs was definitely overweight, but, he was extremely athletic. He had really fast hands, and was quick on his feet. More athletic than many heavyweights over the last 40 years.
Depends what is meant by athleticism. I think it means different things to different people. Take Joe Joyce. Technically, physical strength and stamina are types of athleticism, areas in which Joe excels. However, I think when some people mention athleticism, they mean the explosive type of high twitch muscle fibre athletes, like RJJ & prime Tyson. In that sense, Joyce is probably the least athletic world rated current boxer.
Has to be Michael Spinks. Even in his prime his back development resembled that of an out of shape office worker. Not impressed at all, and Tyson revealed his flaws in like 30 seconds.