If there is plenty of reason to have a black mage, what is it?
Because they have an intended purpose and they do it well? Do you invite a DRK because they can cast black magic? No, you invite a BLM.


... you know what, this is going in circles.
This really isn't going in cricles. This doesn't mean what you seem to think it means.

The job gets played and used regularly for various content its abiltiies can be useful in. Just because it isn't necessairly the star of the show and used in all content everywhere at all times, doesn't mean it needs fundamental changes.

It sounds more like BLM isn't good enough *for you,* not that it isn't good enough in general. Several jobs have only niche uses, but they really shine in those use cases and it generally isn't a problem that they aren't used in all content because almost all of us level at least a few jobs.