I don't necessarily think you need to be a dominant running team - even though it certainly helps - but you can't have a complete lack of a running threat.
If I were the DC against Dallas, it would be simple: Drop seven every play, double CeeDee, tell my Dline to attack up the field, and not worry about run lanes. Dallas' below-average RBs just aren't going to hurt anyone even if defenses are completely focused on the pass. Even with a hobbled Pollard last year, teams had to, at least, respect that he was a legit NFL running back. This year even Dak isn't a running threat, which makes it even worse.
Being so one-dimensional makes it hard on everyone: the QB has less time, fewer passing lanes, and fewer open receivers; the Oline has to deal with DLine pinning their ears back every play, the receivers have less space and DBs that are not focused on the backfield at all.
This is just so simple. I don't get why Jerry doesn't get it.