I don't know that I agree with that.
I'd put guys in groups like this...
Good - Jackson
Serviceable- Davie, Cockrell, Rose
Solid + improving - Kalu, Jones
Could be studs- Anderson, Lee, Mosley
I don't agree with all this and think a JUCO if he comes in and plays right away is a smart move... Jackson is perceived to be good yes but has never played a meaningful snap on D. Davie Cockrell Rose haven't impressed but have been like you said, servicable. Kalu is a stud in the making but Jones is a special teams player so you can't say he's solid. But the 2015 recruits plus mosley do have a lot of potential but a JUCO with experience could help a lot