Since that phrase "offense puts butts in the seats and defense wins championships" was coined, the game has changed. Back then of you wanted to know the teams that didn't make the playoffs, just look at the top ranked passing teams.
The last 3 great defenses, 03 Bucs, 00 Ravens and 85 Bears were considered shutdown D's. However, those 3 teams scored 48, 34 and 46 points, respectively, to win their rings while holding their opponents to an average of 12.7 points. So, none of the 3 were strictly D teams with anemic O's, they were balanced with a lean to the D side.
It's all about balance because a team will have to make a crucial drive or stop one along the way to the SB. The Cowboys have had too much imbalance over the last 15 years. The GM is a follow the ball GM but he got to see some excitement over his D and particularly, two young LB's so the entertainment value shifted some to shine the light on the forgotten part of the team except when Ware was around.
The Cowboys did not have a good enough O this season and in the divisional game, not a good enough D. But it was their D that got them to the playoffs but it was not good enough to carry them through considering the best two teams had the best two offenses. It is not enough for your D to stop them, your O must make them pay.