Most people expected before the season they would win 9-10 and win the NFCE. And those same folks expected a one and done playoff. In that regard, the neither over or under performed.
The problem is the came out of the gate and played the defending champs extremely well in a loss and followed that with 6 straight wins. That ramped up expectations, including a SB by some. In that regard, the under-performed.
I voted based on my personal preseason expectation, which was 10-7 and winning the East. I had no expectations for what would happen in the playoffs because there are too many unknowns and too many games to play before getting to the playoffs.