Is Necromancy in-universe?

[Enkidoh]

People do seem pretty wiling to let the WoL do whatever considering how quick they are to dismiss the unnatural event that occurred because of them at the end of the 1-50 DRK quests.

That's about the worse we've put anyone through because of our job-related shenanigans, though.

There is a difference between the fomerly forbidden/illegal Jobs the WoL is granted like WHM and BLM to necromancy though: WHM is only illegal because the elementals dictated it so after the Sixth Calamity due to the Amdapori using it to create life itself (which they used to animate their statues used as guardians in Amdapor), that the elementals regarded as an affront to nature (while entrusting the knowledge of the art to the padjal for safe keeping). Needless to say, the White Magic the WoL uses is merely to enhance their healing and they're not delving into the 'forbidden' aspects of it.

And BLM is one step up from THM anyway (as ironically THM evolved from simple spells the Order of Nald'thal used in their funeral rites), only really differing by how the spells are generated (THM uses the caster's own aether, BLM is like CNJ/WHM in using the aether from the surrounding environment). Even DRKs are semi-legal being effectively the secretive 'watchers of the watchmen' who administer justice to those in authority considered above the reach of normal means of law enforcement (read: Ishgardian nobility), but because of their clandistine nature, 'normal' law and order regards them as vigilantes at best and dark-worshipping murderers at worst.

Necromancy on the other hand, is an abomination because it involves using the powers of the Void, that alone proscribes the art completely, let alone the whole 'reviving the dead' thing which, as previously mentioned, it actually not what Necromancy ends up doing, instead summoning a Voidsent to inhabit the body of the deceased turning it into a monster like an ahriman or mindflayer - an entire Calamity came about because of a nation using Void spells against their enemies and given we spend a lot of time cleaning up the mess of others who foolishly mess with summoning Voidsent (under direction from authority), it's pretty clear-cut that Necromancer will never be a class available to players. That's just being realistic.