Marinelli may be considered a rain maker, but what is the harm in making his job even easier by adding talent?
I see it like this:
1. Marinelli is going to rotate his DL, period. He just believes in keeping everyone fresh and I agree with that idea.
2. On run downs, he is probably going to have Hayden in there because he stops the run as well as anyone on the team. He might not be a star player but he is more than fine against the run.
3. So, had Dallas drafted Malcom Brown in the first round, he would have primarily seen snaps in the nickle/dime.
4. However, Hardy, Mincey and maybe even Lawrence will be rotated into the 1-tech spot in the nickle/dime packages, and any of those 3 are a superior pass rusher to Brown.
5. So, if Hayden is as good a run stopper as Brown... and Mincey, Hardy, and Lawrence are better pass rushers than Brown, Dallas didn't need Brown very much.
6. With Brown not really being needed, the team would rather strengthen the secondary where they really didn't have anyone who could rotate there from another position.
By adding Gregory, they made it where one of Mincey, Hardy, or Lawrence could move down to the nickle 1-tech spot and Gregory could play the designated rusher spot... So they strengthened the DE's, the DT's, and the secondary with two picks (Jones and Gregory). Even though they didn't specifically draft a DT... they still added a body there in this draft.
I would like to add that I understand where you're coming from and I did like M Brown as a player... but with the defensive staff thinking like I outlined above, I also very much understand their line of thinking as well.