These "worst hire" debates have to consider the circumstances under which the school made the hire.
Dooley took over a program that was already in decline after the previous coach left at an unusual time during the offseason, and that coach had only been there for one year himself.
As OBB suggested Dooley is probably one of the most inept and in-over-his-head HCs of a major program in recent history, but that doesn't necessarily mean he was the worst hire ever. I actually believe that Dooley was one of the better, if not the best, candidates who was actually willing to take the job. Believe it or not he actually had attributes that made him a more attractive candidate that anybody else they asked: he had head coaching and administrative experience, had coached with Saban, and had a good last name.
If not Dooley, I bet we would have had to hire some totally obscure, no experience position coach or coordinator, and that might have turned out even worse. Dooley was terrible but at least had some experience. I bet the other options were just as bad but with no experience.