They are not wrong about the Cowboys being front runners. And they are not wrong about them being built to play with a lead - all though I don't think they were built like that, I think it is the mentality of players that makes them play like that.
Take a guy like Diggs. His mentality is to take chances, to bait the QB into throwing an INT so he can jump a route and pick off the pass. But in a situation like a 3rd and 6 when the defense needed a stop, he needs to be on the receiver looking to stop the receiver from catching the ball. That's as good as an INT. But instead, Diggs let his guy get separation and he couldn't recover in time to defend the pass. It's the same mentality with DLaw and Parsons. They jump inside looking to make a great play only to see the offense run the ball right where they were supposed to be. They do it all the time because they don't know how to play any other way. Micah talking after the game about "we don't need no superman", was referring to this mentality - except he is as guilty as anyone.
Belichick used to say "do YOUR job", meaning each player handles his assignment and success will come. The Cowboys defense has never played that way.