Maybe this will clarify it for you. Auburn went in the toilet after Roof left, not because Roof left; but because he wasn't the problem. The problems at Auburn was much deeper than "fire Roof", the problem at GT is also much deeper than "fire Roof". Firing Roof did not fix the problem at Auburn and firing Roof will not fix the problem at GT. If going through 3 defensive coordinators doesn't show you that the problem isn't the defensive coordinator then I can't help you. Your solution is like replacing a light bulb when the power is out. It is the only solution you know so you keep replacing light bulbs (DC's) even though the same problem persists.