In our scheme and most 3-4s, we don't have defensive ends. We have three tackles when we play base. Our 'ends' lineup as a 5-technique in base. In the 'eagle' alignment, one of those 'ends,' normally BJ when they call this defense, slides down to a 3-technique.
All of our linemen are run defenders first and second. Wilson, Raji, and Pickett are the perfect group to trot out on running downs.
Raji played a fair amount of 5 tech last season, especially early in the year. It didn't work out so well. You'll see him on the nose and Pickett at left DE most of the time in base. In nickel, Pickett sits, with Raji and one of the other DEs at 3 tech. Pickett is Raji's backup at NT, and gives him a blow from time to time in base, though I think Raji's snap count is still very high again this season.
What most teams look for in a prototypical 3-4 DEs these days is a guy with reach to work off OT blocks to the inside or outside. Usually the reach comes with "tall"...6'4" and up is what most teams look for. The 3-4 DE also has to cover a little more ground and plays against the OTs and TEs who tend to be more athletic than the interior linemen, so 285 - 300 lbs. is becoming typical. You'd also like the guy to be able to pass rush from the 3 tech, otherwise you have to always pull him from nickel (on 70% of the plays in the Packer's case).
The three linemen in base 3-4 are not interchangeable.
It is also helpful to keep in mind that the other team doesn't tell you the play in advance. When a team decides to pass against the base D, it would be nice to know the DEs might at least collapse the pocket from time to time. Pickett hasn't been able to do that the last couple of years, and he's gotten very slow to boot.
It's not like TT/MM/Capers don't concern themselves with the prototype...Jenkins was close; Neal is close in physical dimensions, but most telling of all we tried to get Chris Canty to come for a talk when he was an FA before the 2009 season, but he wasn't interested, or so the story goes.
I think Pickett is OK playing against the O's strong side in base, but I don't think it's ideal.
I just think the right players just haven't come along. 3-4 DE prototypes get bid up in the draft. Neal was supposed to be that guy, but the book is open there. I doubt the Packers' ideal game plan is to have a NT playing LDE in base...it's just worked out that way with the personnel on hand. Pickett's effective against the run, but you'd like a little more than that out of the position.