Here is my problem with what the Cowboys do. You can win either with size and Power, or speed and strength.
Both ways will work.
If you use size and strength on the DL, then your DE's need to get the sacks, and your LB's can use speed, more than size and strength.
If you use speed on the DL, then you need bigger LB's to be able to stack and shed because it is easy to wash out the DT's, and you know that your bigger IOL will eventually wear them out.
Get bigger but slower, and OC's go fast. Get faster and smaller, and OC's run on you. You need freaks who are bigger/stronger, and faster.
DQ's scheme seems to prefer the faster guys because it is passing that usually beats a team. They have just decided to accept that teams will run on them. They just don't have the talent to flip from a defend the pass to a defend the run team, IMO. They utilize a SS (Kearse) as an undersized Sam that covers the TE and helps in run defense, and swap the position with DWilson who also jumps in and out of a hybrid SS/Sam role.
So if you were an OC, what would you do to beat the Cowboys?
I would run on the smaller DT's, and after getting an initial move out of the DL, try to get my OL to the second level.
And I would throw shorter, quicker release passes with the occasional screen put in. When they adjust to stop the shorter routes, take my shots deep.
This is what you are seeing teams do to Dallas for the last few weeks. Dallas is just outscoring them. The bottom teams just don't have the talent to keep doing this all game long and they keep making mistakes. Which team that we play in the playoffs is going to stick to the run and just run it down the throats of Dallas? If Dallas had a thumping MLB, he could make up for lots of the lack of size on the DL. If Dallas had more size on the DL, then their LB's would be even better than they currently are -- especially if they could get a player that could allow Parsons to truly play either line or LB, which is only possible if you have a DL that can do the same or a LB that can do the other things Parsons is needed to do.
I really do like the scheme and personnel of the Dallas D except for DL and MLB. They have the DE's, they have Parsons and Clark which are dynamic with their speed. They have very good safety and CB play when everyone is healthy. They really just need one unique hard to find MLB and a talented DT or two to become elite, IMO. Then stop stunting yourself out of the play.