There's plenty of data reflections. From this season. Greg Hardy, Randy Gregory, Joe Randle, Ro McClain.
I realize that you present this as a fan, and not an investigative reporter.
Randle needs intense anger management help...but he wasn't beyond hope until he started to take lightly his role as a starter.
Greg Hardy had an attached bundle of problems that included not playing for over an entire season. He contributed at a starter's level, but not at a top shelf level he was previously.
Rolando McClain has a group of mixed reviews, but on the whole has been a stable influence as a middle linebacker. He has some old baggage that he drags along, but the evaluations of staff are paramount as to his future stop gap or role with the present Cowboys.
Randle gone and should be closely monitored for anger issues.
Hardy, is probably gone, with too many locker room distractions for level of play being paid. Unless he comes as a lower end journeymen stTheatus.
Gregory has to now enter a team directed system that monitors him, both on the field and off...but he could swing wildly back around and be a legitimate positive. I'm not holding my breath, but he was described as a real person prior to the pee tests.
But this effect will be negligable when only McClain and Gregory continue into the summer.
The team will need to sign at least two free agent defensive linemen...and four defensive linemen in the draft would be a strong addition to this and next season.
That would project to two outside pass rushers and two defensive tackles that are very strong candidates via the draft.
I don't know where a DE will be taken in the draft. Myself, at the top and with a trade down if needed.
The Cowboys board will have to determine BPA, and whether that is additionally a QB...we all shall see in a couple of months