QB.
I think it's incredibly hard to rank any other group related to the offense until that's addressed.
Why?
Coaches with the game plan not featuring the RBs as much we should have? Maybe not since the running offense was based on zone reads, and the QB is making the read on when to give and when to keep and we know that was not done consistently well with the QB often keeping when he should have given and vice versa. Maybe we could have had more pure run plays that were not zone read, but that would have required more things to install with a team already limited on what they could execute. That also means having some degree of play action, and with the limitations on the QB, that wasn't likely to be consistently effective either. The limitations of the QB impacted what options we had to make adjustments or to try to take advantage of something a D wasn't good at. Until we are able to see what this entire offense looks like with it completely installed, we really won't know what the coaches can do with it.
OL not blocking well? Teams were stacking 7 guys in the box when we had 4 WRs outside, playing 1-1 and cover zero and the QB was still executing a run play and not checking out into an audible for a pass play to take advantage. Asking 5 OL to block 7 on a run play isn't a good strategy from the QB. QB is, in theory, also calling the protections, and sometimes the line was shifting protections in ways that didn't make a lick of sense - i.e. shifting all the protection away from the defenses best pass rusher. I do think this group has some room to grow, especially our OTs, but there's just too many other variables they didn't actually control.
On D, I think we should look at the DL and LBs (inside and edge) together. It's really different from what we are used to from the past 17 years and the responsibilities change a lot in the position groups with different calls. I.e. we used to know that if we lost the edge contain, that was on an 'edge' player (either DE or OLB). Well, in this scheme it appears that sometimes we slant that edge player inside across the outside blocker and expect the ILB to scrape outside with support from the play side safety (Husky or SS, or whatever). Sometimes the edge player does have that outside gap though. We often didn't get this right, with the edge and the ILB taking the inside and it's hard to know which one was out of position without knowing the play call. I started the year pretty unhappy with our edge guys for losing contain until I noticed this re-watching games. I tend to think this was really the ILBs fault since the Edge guys were slanting immediately at the snap where the ILBs are kinda reacting, even if they shouldn't, to the zone read motions.
As for where each group stands, I think Edge LB (wolf) should be ok. Russaw was really the starter until he got hurt so losing Q Rob and Koht doesn't hurt a ton. Pierre looked good in spot duty and the 2 true freshman should be ready to step up behind them for depth. They all need to put on a little more mass though.
at ILB we're losing JJ for sure, and he was very underrated. Campbell is probably gone since he'll likely be top 3-5 at the position. Lawson I thought would be gone also, but with the injury maybe he comes back. Either way we're going to be very inexperienced in the 2 deep since no one else really got many snaps at these spots this season.
Edge DL (Bandit); Latham is gone and I wouldn't be shocked to lose Overton also. Renaud started working in this rotation when we got thin at Wolf and started playing with 2 bandits in some sets. There's a lot of guys back behind him, but not much experience so this area needs a lot of development just like ILB will.
Interior DL; There was decent rotation here so I think once we get more into the system and how it's played differently it'll be fine.