I think missing Raji makes a difference too and that hasn't really been discussed. You have to have some push up the middle - it's the only way to disrupt the short passes over the middle since the edge rushers don't have time to get home. Raji, at least this year, backs guys up 3-4 yards and makes it harder to step into throws.
Also, don't underestimate how good Rivers is. He's 90-60 as a starter with the 6th highest passer rating in NFL history.