I certainly don't dispute that it could have / would have / should have been a significantly better defense.
The big problem, is that the defense, as a whole, was not equipped to be an aggressive, attacking-style defense that Van Gorder kept trying to run. If anything, it was a lot like 2009, where our defensive players weren't chopped liver, but Jon Tenuta foolishly kept trying to run jailbreak blitzes every down. That ham-handed approach single-handedly resulted in 4 of those losses.
Van Gorder's (and Tenuta's) biggest problem, was that he kept trying to run that aggressive scheme, and couldn't bring it upon himself to play a more conservative scheme. If you're a decent defensive coordinator, then it's up to you to realize that some things aren't going to work, and that you need to try alternative methods.