Yeah, I'm sure the defensive decline from November on was the nail in the coffin.
Like you, I thought the same thing. I assumed the pass rush would be consistently good and our Safety flexibility would help to mask the CB deficiency. I do think the main culprit was the lack of pressure with a 4 man rush. Shula didn't adjust accordingly. I think he was scared to blitz more because he didn't want to give up big plays. That back fired on him because we also gave up a lot of big plays.
What is best in life? To crush your enemies, see them driven before you and to hear the lamentations of their women.