NEW HEALER CLASS IDEA!

[Archwizard]

I just can't see a viable way to turn raising the dead into a healer job without it being completely against the mythos.
There's a reason why 'becoming the warrior of darkness' didn't have us actually having any dark powers.

Is there. Really.
'Cuz last I checked, the promo materials for Shadowbringers put a heavy focus on Dark Knights. Including the literal logo image.
A job which turns itself into an undead as its immunity skill.

Bear in mind if you're still focusing on "dark = bad", you've missed the literal plot of the expansion. Dark is not inherently evil much as light is not inherently good, and the two must balance one another out.

There's a reason why they had to differentiate Summoners powers from primal summoning, Black Magic from voidsent, etc.

That's a matter of splitting hairs to give us the same powers, to be honest. Egi Summoning still involves the core principles of Primal Summoning and, spoilers, the Ascians' creation magic; just look at the questline behind Egi Glamouring, where the mental image during the summoning impacts its shape.
Mhachi magic was researched using and fueled by Voidsent. In the very first BLM questline, we literally have to siphon dark energy from rifts to the Void. The BLM quest in Shadowbringers involves attempting to convince the heads of the Thaumaturges' Guild to accept that Black Magic isn't inherently evil so long as it isn't misused -- which is exactly the angle I would expect we would take with Necromancy.

Given the entire PotD storyline, how could you possibly turn that around into a good thing?

Off the top of my head? Ethical Necromancy 101: "It is the natural order for all things to die so that others may live; it is only a matter of when, and how."

A class of death-revering priests who travel around serving last/funerary rites to put the minds of the living at ease, performing seances and Sendings for lingering spirits, consecrating lichyards, slaying Ashkin and grave-defilers, and occasionally performing feats of miraculous healing for those on the very brink ("No, it is not yet your time.") via acts of sacrifice that Conjurers revere all life far too much to dare tread. Specialists in aether transference; those who draw power not from death, but from the entire cycle of life and its natural culmination, draining from the fell living to give life unto the dying just.
The kinds of people who would look at exactly everything that happened in the PotD storyline and go, "This is what not to do. Nybeth Obdilord wanted to pervert the cycle to extend life beyond its natural conclusion, which is a selfish abuse of the power. If we ever catch you doing that, we'll put you to the scythe just like anyone else."

As I said, there's already a lore opening for death priests in Ul'dah with the worshippers of Nald'thal. A god of bartering.
The same city-state descended from the creators of the Trader's Spurn.
So. There's that.

What you'd need is something different, some different type of healer with a darker flavour, but it wouldn't be a Necromancer.

That's the lovely thing about Necromancers: It's such a broad archetype these days that the name could still be attached to any number of different takes.

At any rate, I've been trying to say, to disregard a balance-affecting change purely on the grounds of not being "lore friendly" is the weakest possible justification. Lore changes all the time, our characters are constant exceptions to established "rules" of the setting.

If we were to get a 4th healer, I'd much prefer something with a more 'technologial' twist, we have 3 magic themed healers already.

I mean... healing falls under "Disciples of Magic", mate. That's like complaining the caster DPS we have are too magic-y.