I wrote down all the changes (both buffs and nerfs) I could think of from my last burst of playing Co-op. My main goal with these changes is to address things that either never get used (buff), or that always get used (nerf), or things that are annoying.
Raynor
Reduce Cost of Siege Tank Transformation Research from 150/150 to 50/50
Kerrigan
Fury (Lv10 Ability) folded into baseline kit at level 1
New Lv10 Ability is Improved Hatcheries. Each evolution of the Hatchery costs 50% as much mins/gas and increases the max number of larva spawned there by 2. Larva spawn rate adjusted such that it always takes the same amount of time for the hatchery to spawn it’s max larva, regardless of whatever the maximum is.
Artanis (needs more buffs but not sure what)
Guardian Shell Mastery improved to .75% per point, from .5% per point
Nexus Legate move power field cost reduced to 10 from 25
Swann
Hellion HP increased by 30% on all Commanders that have them (Swann, H&H, Nova) (harassment is an irrelevant strategy in co-op so units designed for this purpose need to be re-aligned in co-op)
Hellbat has +1 Armor on all Commaders that have them (Swann, H&H, Nova)
Cyclone upgrades cost reduced
Cyclones Cost from 150/100 to 125/75, Armor from 1 to 0, Supply from 3 to 2, auto attack range from 5 to 6, Lock on uses auto attack damage (no armor ignoring mods), Damage to 11+3 v. mech, Move speed reduced to 3.94, Health to 130 (matching MP patch 5.012, 5.013)
Zagara
Scourge Queen Prestige only adds 2 additional free banelings and 2 free scourge per cycle (from 4)
Vorazun
Oracle speed reduced by 20%, however, while the attack ability is activated, the speed of the Oracle is returned to normal
Karax
Orbital Strike ability cost increased from 5 to 7
Fenix
Operational efficiency changed to flat 40% cost reduction, from 50%/100%
Recharge delay of Arbiter Suit changed to be the same as the others (mainly effects Akhundelar prestige)
Network Administrator Prestige changed to 40% less damage and vitals, from 50%
Han & Horner
Wing Commanders Prestige Galleons gas cost dropped by 40% from 20%
Galactic Gun Runners Prestige redesigned. Strike Platforms cost 50% as much mins/gas, but cost 100% more supply (from 100/100/2 to 50/50/4). Max count remains 10. Strike fighters leave behind a flare which casts detection where they hit (similar to Orbital Scan) and Napalm damage now effects enemy air units. Theia Ravens disabled.
Air Fleet Travel Distance Mastery changed to Air Fleet and Space Station Duration. Functionally the same for Air Fleet, but also makes the Space Station last longer on the ground.
“Strike Fighter AOE Mastery” now “Strike Fighter AOE and Damage” Mastery that also increases damage
Double Salvage Chance Mastery increased to 3% per point from 2%
Hellion HP increased by 30% on all Commanders that have them (Swann, H&H, Nova) (harassment is an irrelevant strategy in co-op so units designed for this purpose need to be re-aligned in co-op)
Hellbat has +1 Armor on all Commaders that have them (Swann, H&H, Nova)
Death Effect of Hellions reduced to 5 seconds (intention is to make them less of a splash to support reapers and more of a benefit for committing to the unit type)
Mengsk
Laborer Imperial support reduced by 33% (trooper support remains the same)
Royal Guard XP rate Mastery increased from 0.5% to 0.75% per point