1. Brooks - I hope we just let him walk in free agency. He was mostly terrible and I think someone is going to overpay him. Please don't let it be us.
2. Taylor - I have absolutely no hope for him anymore. I'm not saying cut him, but I'd go about free agency and the draft as if he's not going to play a contributing role. Anything he produces is a bonus.
3. Woolen - I don't think he really needs to be "fixed", he just needs to heal. The offseason should be good for him.
4. Dre'Mont - I think he'll thrive under MacDonald as much as anyone on the defense. This is an excellent hire for his chances of improvement from a so-so season.
5. Bush - Another free agent. He was a force as a rookie with the Steelers, but I think injuries took a lot from him. I think coaching will only do so much. I'd take him back at a modest salary though.
Jordyn Brooks - PFF grade 57.3
Darrell Taylor - PFF grade 50.9
Riq Woolen - PFF grade 67.1
Dre'Mont Jones - PFF grade 61.7
Devin Bush - PFF grade 57.5 (

)
Looks like PFF agrees with your Woolen assessment. Jones and Bush seem to be borderline and may be better as depth signings. Brooks and Taylor appear to be just bad, as you said.
A couple of other borderline defensive players per PFF Grades:
Jarran Reed - PFF grade 63.5
Quandre Diggs - PFF grade 55.1