Prime Vitali had no "extreme" muscle mass. He was athletic, not hugely muscular: http://3morerounds.com/wp-content/uploads/2011/09/Vitali-Tomasz.jpg
Vitali's body was perfectly attainable without steroids. He didn't look roided. Not saying he wasn't because I wouldn't be surprised if most top athletes were, but he didn't look it.
The unbelievable combination of size and stamina is the biggest give away. The best example in boxing is Fury vs Wlad with his non stop movement. The best example in all of sport is Billy Vunipola the England rugby player. He is 6ft 2 and over 19 stone yet plays for 80 mins and make more carries than anyone. As a comparison Derek Chisora is 6ft 1 and 17 and a half stone.......
That's the whole point. Its the outrageous combination of size and stamina. I mean no. Pick one or the other. You don't get to have both. You have these 250 pound guys and they take way too long to get tired for a man their size.