Gross has been and continues to be one of the best LT's in the game. This isn't wishful thinking there are numerous statistics to back this up and that he is constantly under appreciated on this site is crazy. He is also dependable, having only missed games 9 games from 149. Opposite him, Bell has been a revelation and is one of the best pass blocker RTs this season. He lacks the Otah immensity in the running game, but he is a much more reliable and complete OT than Jeff ever was. He very much is starting quality if he continues to play like this.
DE. I guess you could have an argument, but CJ is also up there year after year with the best in the league with the pressure he brings per pass rushing play. His run play has been below average this year, but I fully expect him to pick that up as he has usually been very sound against hte run. Talk about the lack of sacks, but this guy brings a heck of a lot of pressure that no one realises. Now opposite him you have Alexander and Hardy who have 5 sacks, 4 hits and 19 hurries between them That is more than enough to keep opposing QBs busy considering how CJ is doing.
These two positions aren't weaknesses and have actually been areas of strength this year... The guys involved are all young bar Gross and he has been about as reliable injury wise as you could hope.
So we have a LT who is amongst the best, a pass rushing DE who is amongst the best and a group of young players who are playing really well. I just don't get how you see that as lacking major talent. CB, S sure, DT definitely, but no thte other two positions.
I am not downing Gross, not at all. But he is aging, and at some point we will have to replace him. Unless you are cool putting a rookie in the LT spot (and I'm not a big proponent of this) then we need some help there. He is a stud, much like Gamble, but what if either of them go down? They are both up there in age.
As for Bell, he has been OK. I think that an upgrade would help at that position. The RT needs to be your road grader, and that ain't his game.
CJ is fine, no complaints there, but we do need to strengthen that position. We cannot continue to hope that late round picks are good enough at the DE position and can come in and contribute as rookies. I am excited about what I see in Alexander, but I am of the thought that you can't ever have too much pass rush.
As you stated, CB, DT, and S are major concerns. The T and DE are not as much, but are extremely important and we need to be addressing them.