The NFL's decision to change rules over the years, and instruct officials to call other penalties more closely in order to open up the passing game - and therefore attract more casual fans to higher scoring games with big plays highlighted in a 30-second game synopsis on SportsCenter - has resulted in a big shift in what it takes to win in the NFL.
It used to be that the key to winning playoff football was indeed a good defense and a strong running game. There's only two teams that subscribe to that theory still playing right now, and neither gets the benefit of playing outdoors in the cold at home. I don't think it's a coincidence that the last two teams to lose a game this year play inside a dome, or that all four teams that earned a bye are either dome or warm weather teams. The Bengals were the only other outdoor cold weather team to win a division this year, and they're out of the playoffs too.