I know leveling up the hard way is not a "sure way" to make people know their job and party role, but it sure does force them to TRY to learn to play properly and to learn to survive. Let's say normal level grinding process is what weeds out the "dumbness" in people (or even weed out the bad player who cannot play properly to survive LOL). No matter how dumb or slow they are, they WILL learn more from playing the class/job properly than from being PL'ed.

And yes this issue is why I am afraid of doing big stuff with random people.