Dooley was bad, but nowhere near #1 out of this group. Ron Zook, John Blake, Mike DuBose, Charlie Weis, Dan Hawkins, Ty Willingham, and Paul Hackett were all worse. Many of those guys inherited great situations and managed to turn things south very quickly.
On paper, Ron Zook's win-lose record is better than Dooley's, but consider how much talent Ron Zook had! He easily had amongst the top 3 most talented squads in all of college football and still managed to go 8-5, 8-5, and 7-5 in his three years. The SEC was also significantly easier back then than it has been the past several years.
Urban Meyer followed Zook and went 9-3 in Year 1 and 13-1 in Year 2, mostly with Ron Zook's recruits. It wasn't a huge surprise, because everyone knew Meyer was sitting on a goldmine that Zook could never use properly.
If Dooley had coached Zook's Florida teams, I think he would've been 8-4 or 9-3 at least. Maybe even 10-2. It's hard not to win with all that talent. It's likely that Dooley would've been good (but not great) for 2-3 more years, and then would've slowly deteriorated. But Zook was so terrible, he managed to take some of the greatest talent assembled in college football and would still lose 5 games every season.
Dooley was a poor coach, but let's be honest: he inherited a bad situation. His biggest sin was not turning it around, and in fact, making it slightly worse.