The D-line is the most important, IMO. Pelini's defenses have always been at their best with a great front 4 to lead the way. That was true when at LSU, and at NU when Suh was here.
Since then.....not so good.
Zaire Anderson is a BEAST! Reminds me of Terrell Farley from back in the day.
My biggest concern is the defensive end position. I'd REALLY like to see some guys with the ability to rush the passer. Our DEs look sluggish and not even particularly strong. We've had some pretty damn salty ends (Wistrom, Rucker, Tomich, both Kelsays, etc) at Nebraska, and I'd like to see someone step in and re-establish that tradition. I want more aggression from this position.
I think Pelini can game plan against anyone when his chess pieces are as good as LSU usually gets.
I'm not sure the defense NU's running requires/expects/lends itself to dominant pass rushing DE's. Either NU has had some poor ones the last few years or the way NU wants to play does not include turning the ends loose on the pass rush.
You're probably right about scheme, and that is a source of frustration for me. With the interior guys playing two gaps each, I'd think there could be more flexibility/creativity when it comes to the DEs. I'm not the one getting paid to figure it all out, though.
Then again, it's possible that we're just not that great at the DE position right now. I think that in the "old days" Fisher would have been converted to DE. Unfortunately, there was a more immediate need at LB. I know it's been 4 years, but we're still working on building quality players and depth at all positions. You can only recruit so many players each year. I hope we keep getting better and more consistent across the board.