Lesnar clearly has not been the same fighter since he was sick. I don't know if it's an actual physical deficiency, or whether do to having a near death experience he lacks the "killer instinct" or whatever.
I've heard a lot of people say this or things like this because he hasn't fared too well in his last couple of fights. Do you honestly believe he was a better fighter when he was sick? He has improved his game considerably from where he was earlier and is a better fighter now than he has been at any point previously.
I think the answer lies in the fact that Lesnar is now facing stronger, more threatening competition. Even though he has improved a lot, he still hasn't fixed many of the holes that plague his game. Of course when this is obvious, the greater, smarter competition he faces will exploit these weaknesses.
With Cain Velasquez, myself and many diehard MMA fans predicted he would destroy Lesnar ever since this match was announced. Cain is just a way better mixed martial artist. Brock actually came out pretty aggressively, but it's pretty hard to have that killer instinct when you're getting your ass kicked by a much better fighter. Shane Carwin is a relatively similar fighter to Lesnar but with much better stand-up skills so it's no surprise that he had success against him. Lesnar survived because Carwin got excited and exhausted himself trying to finish the fight, then the round ended and Brock recovered.
Now looking at Lesnar's notable wins. He defeated Frank Mir, a guy who wilts when he gets punched in the face or pressured and whose only real threat to Lesnar at the time was submissions. Mir has improved a lot since then but I still think he's overrated.
He beat an aging and completely undersized Randy Couture.
And Heath Herring? He is and always was a mediocre heavyweight, even in his Pride days. I was surprised UFC even picked this guy up.
Not to downplay what Lesnar has done but why can't people accept that he just isn't a great mixed martial artist, and likely will never be one. That being said Lesnar is talented and uses his strengths well, and I believe he can still beat the majority of UFC's heavyweight division.