Talent is certainly the biggest problem and injuries are also definitely a factor but if we're talking about what to do with subpar players I much prefer the continuity to roster churn (which, incidentally, is what they do on the offensive line). If you want to upgrade Darius Butler, James Sanders and BMW (who have all started at times since we cut them) be my guest and go get a first round pick or a proven free agent who is actually likely to be a material upgrade rather than hoping waiver wire/minimum salary guys (Molden, Ihedigbo, and Barrett) will be an improvement.
What would I do for next year's club? I franchise Talib, I am willing to slightly overpay Cole and Arrington (Arrington may be shockingly expensive and I'm not going more than maybe $2 million per year for him), I keep Talib, Dennard, McCourty, and Gregory in their current positions. If Wilson (or Ebner, though I doubt it) can displace a starter, fine. Chung has been hurt too much too count on so bye bye.
The comparison to the O-line is a chicken / egg thing. Did they keep continuity as a matter of philosophy, or because those guys were good? I suspect the latter; for instance, when Stephen Neal retired, they signed Brian Waters rather than just hand the job to Dan Connolly.
Butler was going to be a fifth corner and provided no special teams value. He was replaced by Molden who plays on special teams. He's since been part of two bottom-five pass defenses, getting cut again in the process. Sanders and Meriweather both were going to cost for mediocre performance; they were basically in the same position that Chung is in now. They've also both been cut subsequently. The Pats also added Dowling, a high draft pick, and Bodden, a proven veteran returning from injury. Neither of those guys worked out, obviously, but it's not like they strictly made end-of-roster moves.
I don't mind your secondary plan, by the way, though that's a lot of money to spend on Talib.
EDIT: I'm not defending the decision to go into 2011 with Josh Barrett and Sergio Brown combining for one of the safety spots ... I don't know what that was about.
Edited by Super Nomario, 05 February 2013 - 08:06 PM.