question about unlocking job

[Iscah]

but having to level every class to 30? it 's a real pain.

You don't have to level every class to 30 before you can take up jobs. You just need to level the one class that becomes the job.

If you want to become a Black Mage, you just need to level Thaumaturge to Lv30 and complete its job quests (and clear the MSQ to "Sylph Management", a level 20 quest).

This was always the case, except that previously you also had to level archer to Lv15. You were never able to become a black mage just by leveling archer, it was only a secondary requirement on top of the main class of thaumaturge. That secondary requirement has been removed, and now jobs progress directly from the end of the relevant class quest.