Coughlin stated they had weaknesses in the secondary and lb corps. But sometimes the players just aren't there in 7 rounds of 32 or more picks.
I'm not sure why you're so concerned with this "tradition" of linebackers. Things change -- the team changes. The Giants have found success with this setup so it's not as if they're doing anything wrong.
But if you want to revisit 2011, the Giants defense was getting it's *** handed to it because they didn't know what the hell they were doing until Reese resigned - guess who???.....Chase Blackburn. Boley also had a career year.
Back in 2007, a great deal of credit should go to Antonio Pierce - yes, a linebacker - for executing Pags' defense. Kawika Mitchell and Chase Blackburn gave them an effective linebacking unit.
The Bears and Giants run a similar system. Perry Fewell worked under Lovie Smith with the Bears and Rams. The Cover 2 requires good linebackers....it's something the Bears understand....it's why they drafted 2 more this year. The Giants signed Dan Connor to replace Blackburn and Boley.
Certain teams value linebackers.....the Giants don't, and the Giants defense also happened to suck *** last year. Go figure.
I think the rationale behind beefing up the trenches (especially with 9000 DTs we have on the roster right now) is that our run defense faltered at the line. If the line is able to plug the gaps, the linebackers won't have to defend against the run nearly as much, and we can use more 3 safety set to defend the pass...