I'm sorry, but that's just not how it works. Again, I am referring ONLY to defensive ranking in terms of yards allowed. The Bills may well be a better defense next year in terms of points allowed or other measures, but they will not be the "#1 defense" because this is based on yards. It never works this way in the NFL. When you have a great offense, you typically have a middle-of-the-road defense statistically.
Again, the Bills do have a great defense. That is not at argument.