I had one come in on a Migrant wave. She (I think) hasn't been an issue until recently. I've had her do all various tasks and even tried out being included against a goblin seige as a Marksdwarf. During a savescummed test, I had set her up as a marksdwarf during a goblin seige and she raised a goblin but it didn't seem to do much against anything else, was just still mad at my dwarves and my Dabbling marksdwarves were doing little to nothing shooting it so I decided to retry it without having the Necro as an active military dwarf.
Recently though, the lack of positive thoughts have caused stresses and now has had a tantrum (nothing raised thankfully) and a depressive state while chained up, all the while going through reliving the death of another dwarf that slid into depression and had stopped eating. For some reason, the Necrodwarf keeps complaining about family and friends but doesn't have any family (and as such can't be exiled) and won't socialize. I'm thinking of tossing her into the bridged up section of my fort that has a vampire manager and see if doing nothing but staying in a generic temple branch, military training and doing nothing else helps.
After 10 years, I'm trying Dwarf Therapist so have been learning to read the thoughts and needs a bit more.
I also had a Giantess bring in an Artifact slab that has the title "The secrets of life and death" so I'm considering if I want to try experimenting with it on more dwarves or if I should chuck it in with the Necromancer and vampire and slowly feed them unhappy dwarves. For some reason, nearly all of my migrants in this session are herbalists, animal caretakers or a combination of both which has been really annoying.