You write like you haven't been watching or just refuse to believe what is there to see, IMO. Not that you are alone in this, but still the above is kind of out there.
You point out Jack Johnson in Columbus.... he was a +2, led us in hits and had zero giveaways or penalties in a 5-2 loss. What an idiot, ey? His play was such, that when Dumo went down early the next day, Johnson played +26 minutes in St.Louis, second only to Letang.
No team has six great D-men, and when despite our injuries and poor Murray goal tending, the D is as effective defensively as we have been, you need to credit that D more. After all among those you do rate, Letang has lost 8 games and Dumo 7... and we have trucked along rather fine when they weren't in the lineup.
Having said that - I think both Petterson and Schultz have been mediocre tending to poor defensively. Those are the two among the starters who need to get their stuff right. Schultz has some injury excuses. Petterson.... not much. This is not helping the contract he is likely to be offered early in the new year.