Hiring a DC involves an entire staff shakeup that's going to be a disaster.
You obviously can just fire Patke and hire a DC/LB coach and then assign someone else on staff to Special teams. Then your special teams are still a disaster.
You can fire Patke and Aristide and then hire a DC/LB coach and a ST coordinator and have someone else coach Strikers (assign the position group to the LB coach or to TRob) and then you just sacrificed one of your better recruiters that you just brought in from Texas A&M and doesn't deserve to be fired. In order to hire a DC - 2 guys have to go. Patke is the obvious choice. After that your weak links are Field, Aristide, and DVD in that order. 3 of your 4 best recruiters - that all 'specialize' in recruiting south Florida.
We've shuffled through 2 OCs, 2 DCs, and soon to be 2 ST coordinators and the best hit we've got on any of those is an offense ranked in the 30s. At some point you just axe the guy that's made those hires. The rate he's gone through staff can be viewed as good - because he's making necessary changes when needed - or bad because he can't hire the right guy. He's expedited his tenure and expedited his own expectations - we've all seen enough.