You are looking solely at these guys getting snaps at LB, and negating the role on Special Teams, especially given the current status of the CB position. They are using guys like McDonald, Joyner, Gaines, and McLeod all on the kickoff coverage unit. Not sure having all of your starting DBs covering kickoff is what they want to do.
I also think LAST YEARS snap counts for the backup LBs is irrelevant. They had 3 ROOKIE LBs who were all converted safeties and were here solely for their ST contributions (with the exception of Ogletree). That isn't necessarily the case this year. They signed Herring, who has experience in Williams' defense. Bates has progressed and is no longer considered a liability at the position. And McFadden is not a rookie. Does that mean they put all 6 on the active roster every Sunday? Doubtful. But they now have options in the event Dunbar is still banged up.
There is also the issue of the "off the field" stuff which has been mentioned here. It seems that Fisher is finally taking a stand and holding players (especially fringe players) accountable.
In IMO, the roster is in much better shape today, than it was on Sept 7th. They have all 5 WRs healthy, and once they get healthy again in the secondary, I anticipate another late season run, which Fisher's teams are known for.