What's really hurting the Cowboys in the Wild Card race is their conference record (6-4) as opposed to the Lions (6-2) and the Seahawks (6-2). It causes us to lose three-way ties involving Seattle, and hurts us in the tiebreaker against the NFC North 2nd place team.
It's very likely that two NFC West teams will be at least 11-5, most likely Arizona and Seattle. The Eagles/Seahawks game next week is interesting because an Eagles win may be better for the Cowboys overall playoff hopes - it's clearly better for their Wild Card hopes. I'll be interested to see what FiveThirtyEight's weekly Playoff Chances chart says about that game for us.
In the event that the Cowboys don't win the division, we need to root hard for the Lions to lose to one of the bad/mediocre teams they have left on their schedule (Tampa, Chicago, Minnesota) before their finale @Green Bay. If the Lions lose out on the NFC North at 11-5, then the Cowboys could very easily miss the playoffs at 11-5 if they don't win the East - we'd be then be hoping for some help from the NFC West, in the form of a total collapse by the Cards, or the Seahawks taking two more losses.