It is all about the breaks. Dallas is as good as any team in the NFL and has a legitimate shot at winning the Super Bowl.
Look at the Colts. They're undefeated but easily could have a worse record than Dallas. Last night was a perfect example. Garrad made a terrible throw right to a Colt DB to lose the game. The DB did make a nice play but there was no pressure on Garrad forcing it. It was just a break for the Colts but again, the Colts were able to capitalize on the error so it's not just dumb luck.
Look at Dallas' losses. Each game was realistically within one play, with the possible exception on Green Bay. A dropped pass here or there, a bad call, a missed tackle or one miscommunication between the QB and WR could have resulted in a 13-0 Dallas team.
Dallas needs to catch a few breaks and capitalize when they do instead of missing field goals. It's really that simple.