Let’s put this a different way.This is atrocious logic. You're taking away the toughest opponent this year and the weakest opponent last year so you can call all the others "a wash". That's faulty analysis. You should look at them in order:
The 49ers are significantly better than the Eagles.
The Seahawks are significantly better than the Cowboys
The Rams are significantly better than the Giants
The Cardinals are moderately better than the Redskins.
All 4 out-of-conference games next year will be tougher than the 4 they played last year.
If the patriots played the exact same schedule this year as last year but played the 49ers instead of the redskins, my method says their schedule got harder by the difference between those 2 teams.
Your method says slot the 9ers behind the chiefs as #2 and drop every other team down so you are comparing to a different team instead of the same one. It makes no sense.