As the title indicates,

I would like to see a couple of evil themed jobs and classes. I know BLM is somewhat dark themed but it just doesn't seem to be completely devoted to depraved use of forbidden magic.

Dark Knight is a start, maybe get an attack called dark wave? Who knows. They could easily add something like scythes to marauders to create DRK with.

I always saw blue mages as being more depraved, Quistis Trepe being among those who had an obsessive nature about them despite their collaboration with heroes.

Red Mage shouldn't be considered evil in my opinion, though I gather that is where SE will take it.