I think you are wrong. I don’t think he is fine. At all.
Please play with me 100 games. I am certain i can destroy your opinion utterly and completely.
Many years ago he was my favorite commander… i played him more than all other commanders combined. Not any more. Whatever you may think about my skill, i have played karax for longer than sub level 500 players have played SC 2 coop in total… hundreds of hours for sure.
Playing with any decent ally (except swann) you will feel like sitting in the back seat of a car that drives without your interaction. Sure you can throw some SoA abilities to feel like you are at least somewhat useful… but in the end, Nova does not need you. Not even a little. Neither does Tychus. Neither Dehaka or Kerrigan or Zeratul or Abathur or Mengsk …
Even commanders many consider as weaker - like raynor or alarak - far outperform karax offensively, when you play them well enough.
Karax excels really only in one thing: static defenses and orbital strikes for certain hard mutations… and even there swann can perform similarly.
Karax is one of the least played commanders for a reason: he is worse.
He has sooooo many aspects that should attract new players like a magnet… strong static defenses, instant SoA abilities on demand, auto repair for every unit and building, chronoboost across the board plus chrono wave, etc. etc. But you almost never meet any karax player.
Do all of them suck? Or is there maybe a different reason?
In my opinion it is because you can perform better with the SAME skill playing a different commander. And that is true, wether you are a mediocre or excellent player. A same skill Nova will do pretty much everything in the game faster and better than you. Same for Zertul. Same for Tychus, Dehaka etc.
Playing as karax, is basically being permanently broke all game long. His units are so expensive, that you can’t even produce from 2 stargates permanently. A decent Rynor or Tychus or Kerrigan will be banking thousands of resources late game. Not because they are bad, but because they are maxed. This also means that they can recover from loosing a decent chunk of their units… karax cannot. Never.
All the last years the power creep has pushed commander abilities forward, yet karax has stagnated. Other commanders get buffs… what does karax get? A mastery that brings down his unit cost to ALMOST normal price… gets REMOVED and replaced with an HP mastery. Glorious.
Now karax has tougher units, but LESS. If you managed to keep your units alive before, the new mastery does NOTHING for you. You have less impact on the game, no matter how you look at it. Less units equals less damage, less mirages to lift up enemies, less energizers to buff your army or reclaim enemies, etc.
That is worsened by the fact that karax already has a horribly slow ramp up. You never reach even close to max supply with any decent ally. Many times you don’t even reach max upgrades before the game is over. And that in the face of improved chroboboost plus chronowaves. That’s how broke he is.
If you still doubt what i am saying, ask yourself this: imagine each commander being played by an EXCELLENT player each. Lets say they all 2 base solo rush a coop map like Rifts to Korhal. Which commanders do you think the karax player can beat in time taken to win?
If you ask me, i would say: none. No commander would be worse than karax. I think even stukov would win despite his need for creep.