Win comes 1st, everything else 2nd. So an other factor is the opportunity cost. A player with 13 OD and nothing else in my eyes will not be as useful as a player with more balanced training.
a OD only guard could be still effective, i know a team who run this strategy quite succesful in div 2 with low salarys an a inside attack strategy ;)
But you are right about winning, especially because OD/passing are probadly the skill who you should train at last for the elastic effect(at least if the theory is right) and driving is the skill who you should train first. I personally rate driving pretty low, but a driving only player who could vcreate his own shot but rarely could finish a open one is probadly worthless in the eye of the most managers. And for optional training you had to train the guards alot on Point Guard position, so normaly i recommend training OD(imho the most powerful guard skill) and Passing(which you need when you play him at PG) first.