Dubas has shown himself to have a good eye for talent and surrounding himself with others who do as well. At the OHL that is far and away the most important aspect of the GM's job. Since players are in the league for such a short time, drafting is far more important than in a league like the NHL (still important, but many other aspects increase in importance there).
If you want to be a perennial contender in the OHL, you need to draft well every year. The rest is gravy. If Dubas was here but without Keefe, I have no doubt he would have success.