Per GD, the DL is the same as OL.. the particular lineup is assessed as a unit, not individually. This means, that while you put your stud at DT he might be a monster to a team that runs inside, ,but if they run outside, the DE will get the tackle and vice versa.. The notion is the same for the OL. you can put a lineman in that has 90 strength and only 80 blocking in at the interior, (center, guard) positions and put a lineman that has 80 strength and 90 blocking on the exterior(tackle) positions and they will equal out. I don't agree with how GD does it but that is how it is done as of now.
Atleast this is how I come to understand the game.