Nybeth Oblilord from PotD is a necromancer, summoning undead (and you know their undead because Kiribu hurts them significantly while also making them disappear permanently), his goals ain't horrendously evil, just wanting to prevent death but he was willing to do it by any means, Edda was just another experiment to him, she died in Tam-Tara Deepcroft but her spirit was taken by Nybeth to do his bidding furthering his research, we set her spirit free when we kill the puppet form of Edda on floor 50.
The whole thing is frowned upon heavily, bare in mind while not necromancy, doing the exact same thing of using a dead body to call forth a voidsent slave is abhorrent to the people of Eorzea so using the dead in any shape or form without their consent is going to be heavily lore breaking for the WoL to be.
You can have a Necromancer esque job but it has to do away with forced servitude of any kind (skeletons/zombies etc) or anything that can be perceived as desicrating the dead, think more Shaman/Shrine Priestess than Necromancer and at that point it ain't Necromancer.
As for Summoners they were reviled in the 3rd Astral era due to some of them using their powers for their selfish desires (the few ruining it for the all) and people got it into their heads that anyone learning to be summoner is going to be evil.
The lv50-60 questline tackles this history repeating again with Tristan's brother, who was dead btw (killed by Tristan's hand sending him down the path of Evil Summoner for lv30-50 questline) and 'revived' as an Ascian pawn, so there you go another Necromancer, Ascians.
You could argue Ellie from Hildabrand may have been a necromancer as she commanded zombies to attack you but you could also argue it were the trinkets or a side effect of the Trader's spurn that allowed her to be able to control them. Whoever created those zombies that found Hildabrand were 100% necromancers as they all had glowing tattoos this is clear forced servitude.
No matter how you look at it for necromancer to be a job it will be a far harder challenge for the writers than anything else to not contradict existing belief laws the game currently has.