I think that the defense did a fantastic job overall, outside of those two unfortunate situations where they were forced into short yardage/red zone drills by turnovers, and there were some standout performances in all three levels there.
That said, we should keep in mind that while the Ravens are one of the best teams that the Pats have faced this year overall, their offense is in the bottom 5-10 range in the NFL this season. Opponent strength matters when judging how well they did, especially in the context of the discussion around using points allowed as a measuring stick. While I loved a lot of the schemes I saw, rush packages, and the individual efforts (it seemed like the Pats were really flying to the ball), it helped that Flacco made a bunch of bad throws, and the Ravens were pretty one-dimensional on offense from the get go.
Obviously, you play the teams you are given, but it's worth noting that the only above-average offense we've played all year is Buffalo (not counting PIT w/o Ben), and that most of our games have been against the worst offenses in the league. I'm not saying that it means our defense is bad, just that it is very hard to evaluate. All that said, I really did think that they looked like a different unit last night, and they stepped up and made a lot of plays when they had to, regardless of the opponent.