So If I, experienced player and forum writer for 15 years DukeNukem would be “honored” to fix the balance this is how I would do it (and I explain why for each change):
MAJOR CHANGE - ZERG:
Most important thing would be as I say that for 15 years: NERF ULTRALISK!!! Make it a giant TANK ROLE, not an INDESTRUCTIBLE HYBRID OF TANK-MELEE ASSASIN WITH INFINITE ARMOR AND SPLASH DAMAGE. So first good step would be reducing its armor by 1 or 2 points. Then removing splash damage from ultralisk attack and then slightly increase the HP. So it would be still a good tank (a bit worse VS units with low DMG) and even better against some heavy hitting units (because more HP) but it would be still killable by units like marines in extremely high amount. I understand ultralisk is supposed to counter these units but watching extremely giant balls marines worth like 2000 minerals dying to one or two maxed up ultralisks thrown on a-move is a joke.
Protoss changes:
Very small Protoss nerfs - to restore the balance I would do very small protoss nerfs of some core units. Their firepower is too strong in general. These would be very small nerfs - even smaller than balance team…er excuse me “bananalance team” doing to Terrans for 14 years every single patch. So in general I would just say, reducing a bit of firepower and defensive abilities for the Protoss race. Nothing extreme. Simple reduction of lets say 2 dmg on Stalkers or 10 HP on Zealots would be fine. I would also nerf a stalkers blink as it’s extremely OP ability especially in midgame so I would increase the blink cooldown slightly - I repeat, slightly.
Terran changes:
Bring back old sentry tower, bring back old widow mines splash radius so it can be used as a defensive or offensive unit and not as a joke that can’t even kill 10 clumped zerglings and I would also bring some kind of rebalance of Ghost - a slight nerf to the Ghosts power after Protoss would be rebalanced like I mentioned above. So unfortunately I would nerf my favourite EMP spell a bit by either: giving it cooldown or lower the shield drain against Protoss units.
Short summary:
-ultralisk armor nerf by 2, increases it HP even more (by 50 or 100), remove the splash damage,
-zealots HP nerf by 10,
-stalkers dmg nerf by 2 and slight blink cooldown nerf like 1 extra second,
-bring back old sentry towers (radar range and price - so it would be more expensive but would do its job properly),
-bring back old widow mines splash radius,
-ghost EMP nerf against reworked protoss (higher cooldown or lower shield drain).
It took me below 15 minutes to write this and I fixed the game. I did something that nobody could do for 15 years. Now throw roses.