Yoshida has already said numerous times now they don't want the WoL associated with anything negative in terms of job identity. This is why Necromancer, Thief and etc have repeatedly been shot down. Even Dark Knight's lore in other FF games is a lot, well, darker than the vigilante portrayal XIV has.
So while yes, death magic doesn't have to be evil. The fact most associate it with that connotation means they won't touch it.
