Make level progression stop at 30 and do not go ahead if you still in base class, and the problem will be eased a lot.

Even more insane suggestion: you cannot level up until you do your class/job quest. You cannot level more than 5 levels of your incomplete Main Scenario quest.

Goodbye automated bots! They will be kicked out the dungeons they need to progress, and 90% of them will stay in Sastasha forever.