On the Defense I think that the Merriman did add a lot. He wasn't great in coverage or against the run but what he did best was get pressure on the QB. This whole year the Chargers haven't pressured the QB and that exposes our DBs. Cromartie is more of an athlete than a Cover Corner.
On the Offense I believe that Lorenzo Neal helped LT more than most may think. Being hurt early hasn't helped but I don't think Tolbert creates the holes that Neal would. I also think that the offense play calling is not creative enough. Under Cameron the running game got to the outside using misdirections and counters but nowadays it seems they are trying to do power running which LT can't do. I also think Rivers is having a tough time as they get closer to the end zone. He sometimes stares down his receivers.
Sad thing is, is that they have a chance to still make the playoffs. They have Oakland, KC, Tampa and Denver left while Denver has KC, Carolina, Tampa and SD with a 3 game cushion. If Denver goes 1-3 in those 4 (a good possibility with how up and down they have been and how good the NFC South is) and we somehow pull off the Tampa game (I believe Oak and KC are very doable and that leaves Denver at home), we have the tie-breaker. Whichever way, I will continue to root for them and think "maybe next year".
Thats just my opinion.