Necromancer rework was absolute garbage because they changed unholy frenzy into a terrible spell which no one asked for. Cripple cost 80 mana and Necros do not even spawn with enough Mana for 1 Cripple.
Cripple needs more stat tweaks and a special setting which makes it so a unit cannot benefit from movement speed bonuses like speed scroll or speed auras, to go above a certain movement speed. -> Boom, immediately you add an option to use this unit in UD vs Orc and UD vs Orc has been a terrible matchup for UD for many years. Everyone knows it, the best Orc in the world calls the matchup “easy peasy.” Now thats how you make balance changes. Took me only 2 minutes to think about and come up with.
Necromancers and Frost Wyrms still need an overhaul.
Gargoyle AI is still not fixed so UD has no proper anti-air besides Fiends with web.
If the dev team would just focus on one aspect at once, have players try it out on PTR, with different iterations like the Starcraft 2 team does it, it will work. The Starcraft 2 team offers 2 different unit changes to test on PTR, which has worked well in the past. The way the Starcraft 2 team does balance is great.
The developers (or whatever janitor is managing the game atm) just needs to look at what SC2 devs are doing and repeat it.