I'm not a Lesnar fan, but I will give him some credit. I think his athleticism, especially for someone his size, is amazing. I also think he has extremely good wrestling skills and is a powerful striker. He also didn't have that big of a weight advantage over Mir or Herring. Both of them fought him at about 250. Couture he had a large size advantage over. He still has a lot to learn though and he is so new to the sport that it's hard to tell what will happen with him. The Carwin fight will hopefully provide some answers.
True, he is very athletic. 15 lbs over Herring isn't huge, but is signifigant, and I think Mir was at 240 or so. Mir could have done better, but I don't think he takes his conditioning seriously enough. He even said he hates cardio.
I wonder what the difference is between weigh-in day and actual fighting weight for most of those guys.