As It Stands, Mortal Ray Seems Nearly Worthless.

Casted it on a level ~15 crab in the dunes as level 91 BLU with 420+ magic skill.

1/3 landed. That is horrible.

I would rather see SE lock the spell so you can only use it under Azure Lore and boost its m.acc at least over 50%

The spell costs ~247 MP. By the time you used that MP for an "attempt" at doom, you might as well have casted several better spells (like quad continuum) and killed the mob anyways. In the case of regular mobs they die in less that 90 seconds anyways. In the case of NMs, I bet most are immune to Mortal Ray.