Wash and Philly are both much better than Dallas right now because they're good at offense and defense. Wash has the more impressive wins (at LAR, vs OAK), but Philly has the win over Wash and the better point differential. Of course most of that differential is due to the whipping up on a terrible AZ team at 1:00pm in Philly. Both teams are similar with QBs who are good if given time and space, but mistake prone when you take away time and/or space (although Wentz is getting better at making plays when the pocket collapses, whereas Cousins still struggles). Neither team's built to play from behind, so they're winning due to being up and holding on (like Philly barely did vs. NYG with their 61-yard gw).
Dallas has to go 5-1 in the division and sweep either Wash or Philly to have a shot. As Dallas's schedule is tougher as they still have to play KC, ATL, SEA and OAK out of the division. 10-6 will likely win the division unless Philly wins lots of close games.
The biggest issue for Dallas right now is the spine of their D - the DTs, the LBs and the Safeties. Lee helps some, but not sure it'll be enough or how long he'll stay healthy.