not sure what you disagree with since your points 1 and 2 are exactly what I said. So in your mind that makes a good defense? How about if we agree to call them a mediocre defense?
Your opening statement was "this defense is not very good". I disagree.
I said we are a top 10 defense, and a good/very good but not elite/dominant defense. I would argue that there's a difference between that and "not very good".
Look at the 2003-2004 years. The 2003 defense was the best under BB, giving up a league low 14.9 PPG, leading the league in interceptions with 29, finishing 6th in YPG and sacks, and 4th in run defense. But it still gave up over 30 points 3 times in the regular season (a 31-0 loss to Buffalo in the opener, a 38-30 win over Tennessee, and a 38-34 win over Indy which we only won because we made a goal line stand and stopped the Colts 4 times from inside the 1 yard line). And we gave up 29 points to the Panthers in the Super Bowl, including 3 TDs in the 4th quarter when our elite defense couldn't stop the Panthers and gave up an 85 yard TD pass among other plays.
The 2004 defense finished second in PPG at 16.3, 6th in rushing YPG, 4th in forced fumbles, 7th in interceptions, and 3rd in sacks. But we gave up 34 points to the Steelers and and 29 points to the Dolphins in losses.
Despite giving up 38 points to the Saints and 35 to the Colts, the 2009 Pats defense through 11 games is ranked 7th in PPG at 18.4, 10th in passing YPG, 5th in interceptions and 3rd in forced fumbles. Not a great defense, but a respectable one. And that's with being in the bottom 5 in sacks, reflecting the lack of pressure we've been able to generate on opposing QBs.
This defense is good to very good right now. It should get better, as it is very young and inexperienced. It's not up to the 2003-2004 defenses, but it brings a lot of athleticism, speed and playmaking capability. It has really only looked bad once this season, in the NO game, when the defenders clearly got rattled and flustered.
I think they're better than mediocre. Significantly better.