The Undead factions have three common traits that when combined make them (arguably) the strongest factions in the game and the most forgiving tactically.
1. Crumbling- you know it, you hate it. Every undead unit being unbreakable and instead taking minor damage over time in sticky situations is very powerful.
2. Army wide fear/terror. Undead armies don't break and they debuff other factions leadership as standard. Losing control of your units is always a pain and having it happen in combats you were winning is doubly frustrating. There is no intelligent application you're just getting debuffed and ground down by default.
3. Undead healing. Their greatest asset, restoring models is crazy good and with few exceptions, exclusive to the undead.
So what makes this thread more than just a rant against the undead factions? Well potential changes of course. Some of them are less likely than others but here goes.
1. Crumbling, its annoying but its thematic and I don't hate it I just don't think it should be army wide in each faction. VC as example, zombies, skeletons, black knights all make sense for crumbling, they are animated by magic. Vargeists, Vargulfs, Black Knights, ghouls; they exist without a Vampire or necromancers will they should be routable because they want to unlive another day.
2. Fear. I didn't understand it on TT and I still think it doesnt make sense now. If you live in the Warhammer World, zombies and skeletons are a known threat. You know what is uncommonly frightening for your rank and file state trooper? A 6 and a half foot tall viking encased in armor forged in hell who choked out a demon with his bare hands until it agreed to serve turn itself into an axe for him to use in battle. That is scary. A 70lb skelton with a rusty knife and the coordination of a toddler is less scary than a regular dude with a frying pan. Not every should get fear.
3. Undead healing... can't really do anything about it. It's thematic and an asset but maybe it should apply in the same way as my crumbling suggestion. Bringing back a blood knight doesn't make sense but a skelton or even a ghoul depending on how you think about them makes sense.
I'm looking forward to being scolded with whataboutisms and foppish scoffs.