With regard to your game specific comments. Philly lost to NY when they were down two OLs and Westbrook. The Saints just lost to StL and the numbers don't realize that Peterson isn't there now. Cincy may have beaten the Ravens twice, but they are 1-6 in their other games while Balt is 4-3 in their other games. Should we completely ignore those games?
But, again, you are treating this like it is based on opinion. It is not. Frankly, the only thing that I would take issue with is that NFC teams would be naturally skewed upwards. When you face junky teams, your stats will look better than they would otherwise. Other than that, there is no real reason to contest much of this.