By Matt Ehalt The Cowboys went 12-5 and won the NFC East last season, and their over/under at SI Sportsbook for the upcoming season is 10.5 wins. Regular-season wins aren’t the problem for the Cowboys. No, it’s those pesky playoff wins that flummox Dallas. Dallas returned to the playoffs last year following a two-year absence by winning the NFC East with a 12-5 record only to yet again flop in the postseason. The Mike McCarthy-led squad fell at home to the 49ers in the wild-card round. That home loss overshadowed a positive season for Dallas that featured Micah Parsons being named the Defensiv…