While I agree that some people need help in understanding how a role works, there is a downside to this method that I can instantly see. Development time. Creating anything in a game takes a lot of time and money, way more than you expect. If they were to spend time in developing this so that the minority of players are forced to understand how jobs work, that would be time taken away from a lot of other content (similar to the drought that we are experiencing now). I don't know about anyone else but I would rather see more meaningful content that all the people can enjoy because let's be honest, the vast majority of people you queue with are likely to be pretty solid, or at least not game breakingly bad. They might not be optimal under any circumstance but the job gets done eventually.
If someone is having a hard time try and help them. If they don't listen then they probably won't pay much attention to the trial.
What I believe SE should have done from the start is to more the job quests more of a tutorial then they are. Give the player access to the skills at the start of the quest and design the quest in a way that lets the player understand how the ability works in relation to their current level. It would be harder to develop, at least that way it would be one and done, no development time lost in creating something otherwise unnecessary.