I have not read through any posts yet.
I had told a friend of mine for years, Cowboys don't have a defense. A few years he claimed they did. I said yes it seems so at times. However... they can't make those 4th quarter plays or stops. Teams will come back and score and they lose, or they can't create a turnover or get better field position for the offense.
I still felt that way. Now last years defense showed some signs of that, but still came up short at times. Then again the offense settled for FG's and not getting the red zone production.
Anyway, as you ask about elite defenses. Look at the 2000 Baltimore Ravens defense and their very mediocre offense with Trent Dilfer. With our #1 offense which should be in the top 10, probably top 5 again. Just need to get that defense in the top 5 now, as to playing like it all year long. Not just at the end.