I will now admit to just a bit of disengenuousness. I don't hire instructors from outside my own operation at all. I identify candidates at the ow, aow, rescue level and recruit them into my DM program and the cream of that group get recruited into an IDC. While they are in training, they are, indeed, apprentices, but I won't graduate a DM unless I feel he is ready to enroll in an IDC. My DM program (from rescue diver) averages 8 months, the fastest I have ever had a student complete it was 2 months .
A laudable process, and one I would strive to adopt myself were I in your position. With the LDS with which I work, that is how almost all of us got where we are. There are, however, some people who came from the outside. Those people needed to be judged by their merits before being taken on the staff. There are only a couple, and I only know smatterings of how they got where they are. I can only judge them on what they can do now.