I am still in the early parts the game and unlocking more and more combat techniques and character customization as I go. Despite everything I have learned so far, one thing I am having a hard time wrapping my head around is how certain units "excel" as certain roles/classes. Each unit starts off with their own unique class, which fills the typically fighter/healer/tank role in an RPG.
Initially, it makes sense to leave each unit as their starting class until it is rank 10, and then the game encourages you to try out different classes once you've reached that soft-cap. The game itself does not guide you down a specific path on which unit functions better as which class. However, there are many guides out there that give their suggestions on which class certain units perform better as than others.
What actually determines the "best" class/role for each unit? As far as I can tell, each unit will get the same arts for each class, so are there other hidden mechanics that would derive this?