Not 1, not 2, but 3 sub .500 teams in the top 10. I know everyone was expecting the Cards, Panthers, and Bengals to be really good this year... but they haven't been. The Cards lost to a really good Pats team, beat a mediocre Bucs team, and got embarrassed by an embarrassing Bills team (that you have ranked in the 20s). The Panthers have a bit more of an excuse as their losses have been to mostly good teams (the Broncos and Vikings) but I am still not buying a #5 ranking for a 1-2 team who's only win came against a horrible 49ers team. Lastly you said it all about how the Bengals have performed so far this year. These are not good teams this year, shouldn't their ranking reflect that?
While your brief analysis of the Panther's Oline has a lot of truth to it, I'm not sure it's yet fair to say that their is a problem in the 2ndary. The rooks are playing pretty well and definitely aren't the problem. Another is that they can't get a pass rush because the QBs are having success throwing the ball for short, quick, Brady esque passes, but when throwing deeper, the interior rush at least is getting there, and the corners have been impressing. While they are no Norman at this point, I can say that they are one of the few bright spots so far. The main problem is that the Oline can't block, and special teams can't tackle.
Summary: Ryan Kerrigan is hard not to like with so much production and experience coming out of a major FBS program. His numbers kept getting better, capped off by a senior campaign with 26 TFL and 12.5 sacks for the Boilermakers. Opinions vary on which scheme suits him best, and it will depend on the system. He displays the drive required to adjust wherever he goes. On the downside, his effort might not be enough at the next level.
Player Comparison: Aaron Kampman. This is a common comparison because it makes sense. Kerrigan has more hype coming out of the Big Ten than Kampman (Iowa) did when he was taken in the fifth round, but both are effort players with a similar build. They also both bring all-around value at the defensive end position.