The DITR function is totally random as far as I can tell. I have seen an already elite player get the advantage but it is very rare. Just as rare is the increase actually makes the player viable for the ML. Normally teams that are bad, like the Diablos get four of them in a season like this year. Normal range for that is zero to four btw, don't think I have ever seen anyone get more than four. . Of course it didn't help all that much, just longer careers in the minors maybe which is a bit helpful. I normally hope my DITR's are catchers as they can turn out to be fringe players if their PC gets up to the upper end. I actually got two short relievers which is normal and two starters which is unusual. Still, none of them I consider even fringe players but can be very helpful in the development process of other players and getting the minor league team to the playoffs. One thing to note, DITR's have a tendency to develop differently, especially if they are young. They tend to develop more after the first three years than normal players to reach their potential.
There is the initial DITR jump I like also but you don't get to see it if it was from a just drafted player. One of mine was an International that was signed at the end of last year. I must have thought he had enough potential for the low minors then (and spend spare cash on) but now can possibly make it to AAA. Three were actually minor league vets and that is all they ever will be which happens quite often.