Its not so much a criticism as it is something worth noting. They have found the proper balance and it can continue to work, but in the case that they play a team that shuts down their run game, will they be able to recover. Now most if not all teams would likely lose if you shut down their #1 offensive weapon, but some teams have the defense to keeps games close when the offense is not on point. I am not sure yet that Dallas has the defense to stay in a game like that. Maybe they do and they were underrated all along or maybe they won't get in that situation, but it is worth noting. The game against Seattle was a big test and they passed so they are headed in the right direction.
Shutting down their run game is something that is easier said than done. They've already shown they can run the ball against some of the better defenses in Seattle and San Francisco and they have shown success running against any defensive formation. Everybody knows by now they are going to constantly run the ball, and so far, no one has been able to stop it.
And as @Everlong mentioned above, if the opposing defense sells out to stop the run, that leaves favorable matchups for Romo and his receivers on the outside.