The Pats have made substantial changes to the back end of their defense with the acquisitions of Darrelle Revis and Brandon Browner, but have yet to address the front end. They've passed up a lot of options in free agency.
Thinking more about what a defensive front end would look like that would create the greatest potential, I keep thinking conceptually of a 5 man "base" DL with a NT flanked by 2 "3 techs" flanked by 2 "edge rushers". Seattle used this "Bear" formation quite a bit:
Muth read: The Seahawks and multiple defensive fronts - SBNation.com
Big-T in particular has been a strong proponent of the potential advantageous of overloading on the DL in combination with a dominant secondary. There are several advantages to this approach:
1. It is very strong against the run. With a big NT like Wilfork/Siliga in the middle and 2 DTs on each side flanked by a DE on each side, you have 5 men on the line and terrific run stopping ability.
2. You can generate tremendous pressure up front. You can crash either or both 3-tech with a big NT like Wilfork or Siliga to plug the middle, as well as create pressure from the edges.
3. You have terrific versatility to morph into various hybrid fronts, including 4 man, 3 man, and semi-ameboid formations.
However, this approach puts pressure on the LBs, who must be able to cover a lot of ground and be effective in coverage. The emergence of Jamie Collins is one of the keys in allowing this kind of approach to be effective, but another rangy coverage LB is needed.