You nikkas don't give that Mavs team enough credit.
Marion and Terry got in LeBron's head. Dirk was unconscious and unstoppable that postseason. Tyson Chandler changed the complexion of that squad's pysche. Barea was also ballin.
Game 2 was an epic collapse and the games after before Game 6 could have gone either way.
I agree with you that the Mavs were playing FANTASTIC ball, but i don't think anybody (outside Mavs fans MAYBE) thinks that if LeBron plays like himself, that the Heat woulda lost that series. Sure, he didn't have the post game he has now, but he was just chucking ill-advised J's, and letting Barea guard him in the post. He was totally disengaged. And even then, like you said, the games were close.