They had a great defense and stayed committed to the run. Their terrible division guaranteed them the opportunity for a deep run every year. And they still barely won each Super Bowl, in fact I believe they were allowed to cheat in the first Super Bowl with all the defensive holding non-calls (let alone the fing tuck rule)
Dallas doesn't have anything close to a Richard Seymour or Ty Law, and the competition is waaaay better than the Eagles and Panthers were.
Against the Packers, Falcons, and Pats/Steelers we WILL need our offense performing at a very high level.