1. Remove the fucking Colossus.
The Colossus is the definition of a bad fucking idea. It has 350 fucking health. You can Yamato this fucking thing, and it will not die. But wait, the Colossus can be upgraded to have 9 fucking range. What the fuck is that? This fucking thing has a sea of hit points and yet it can't be hit because, let me say again, it has 9 fucking range. You can't build a game with a unit like that in it. That's why you give this glorified AT-ST the ability to walk up and down cliffs, and did I mention this is no Reaver, it's as fast as a fucking Zealot? Call the fucking Ewoks, deus ex machina we need a deus ex machina.
As if its complete failure from a stats perspective weren't enough, just fucking look at the Colossus. It finds its roots in a Tom Cruise (post-insanity) movie. The Colossus looks fucking hideous. And it's fucking huge. What could be worse than the most disgusting unit design ever created? Easy, the most disgusting unit design stretching across half your fucking screen. As much as you try, you can't not see the god damn thing because it's ten stories tall and as a wide as a Thor.
As eloquently as I can say it: The Colossus fucking sucks. Not only does it suck, but it reshapes the entire game to suck. Five minutes after the first Colossus has been spotted on the field of battle the entire game has degenerated into a clusterfuck. How could it not when the only unit actually doing anything is the fucking Colossus. The Colossus becomes the backbone, heart, and soul of the Protoss ground army, and that's shit. The fact that Protoss ground is completely fucked without the Colossus probably hasn't escaped the attention of the bronze players who are flirting with negative ratings. So get the god damn thing out of the game, rebalance the Protoss ground army and consider putting in something that's actually interesting like, uh, the Reaver, or, uh, anything that has not the faintest resemblance to the fucking Colossus.
2. Remove the fucking Reaper. There is no unit in the game that vies with the Colossus for the title of the worst unit. But if it could be said that there was an aspirant to that lofty fucking distinction, it would be the Reaper. Here's another horrible, non-strategic unit. Why non-strategic? Think about Chess. Limitations make the game interesting. If everything could just do whatever the hell it pleased, you wouldn't have strategy, you would have a god damn cluster fuck. And that's what the Reaper is all about. The Reaper's sole purpose is to convert a relatively interesting early game into a cluster fuck.
New player? Well you better get on board or get the fuck out, because you're gonna lose 100% of the time to this guy. Like his rival, the Colossus, the Reaper can scale cliffs, so he can enter your base from virtually any location. Then he can rape your Marines, Zealots, or Zerglings and finally rape your workers. That's the whole story. It doesn't have a sequel because you'll never see the Reaper again. Nonetheless, any time you play a fucking Terran you better get it through your head that a Reaper rush might be on its way, because if it is, and you're not ready, it's game, set, match. This guy rapes all your early game shit and all your buildings, so you're fucked. You can't hope to kill or delay it with your workers because it rapes all those instantly. Bottom line, if you're a new player, get on the right side of this issue. If you're below Platinum league and you wanna move up, just remember the "r" button, and no, that's not "r" for Roach. It's Reaper time.
The one virtue of this unit, and the reason he shouldn't be in the game at all, is that the Reaper serves virutally no purpose after the initial rush period is over. 50 gas for a unit that has like 50 hit points, 4.5 range, and can't fight anything armored? If you'll buy that for your army you'll buy real estate in Detroit (or are we past this one?). Anyway, fuck the Reaper, for virtually every function it might serve, you have some better alternative. The Reaper's entire existence revolves around fucking up early game build orders and to possibly do a little harassment or expansion denial afterward. That is not the kind of unit you want in your game. Every other unit serves some meaningful combat role. The Reaper does not. The only purpose this unit serves is to give competitive and non-competitive players alike a mindfuck when they're designing build orders. And for non-competitive players, if you're just hoping to sort of build stuff without any real plan in mind, expect to lose most of your games against Terran opponents in about 5 minutes. Fuck the Reaper.
3. Remove air units. Wait, that's not quite it. Do something about fucking air units, specifically, do something about air units blowing up everything on the ground. You've removed the Goliath. You've made Archons suck. I can no longer make a Hydralisk until I have a Lair. If I'm Zerg, my fucking macro mechanic is the only thing between me and the fucking fleets of Aiur. Talk about proof that the whole Darwin thing was a pipe dream, this is devolution if I've ever seen it.
What's more, the Wraith is back and it's called "Banshee." Now it blows the hell out of anything touching the surface of the world - and it does so from the fucking moon. The Scout's gone - oh no - and now we've got the Void Ray. Two of these guys will fuck your world up. Again - new player? Protoss opponent? Expect to see the big blue eraser beam wipe out all your base. And what's even better, Corsairs find their reincarnation as the Phoenixi / Phoenixes / Phoeniii. They'll be throwing shit around with tractor beams. Now even the anti-air will rape your ground forces. And of course the Mutalisk makes its triumphant return, not to have its thunder stolen by any of these other air-to-ground monsters, the Mutalisk is returned in full fighting form and is completely capable of all the bullshit it was before except that now you don't have to micro it because nothing on the ground can kill it.
But seriously, this is how it is. Half the surface-to-air shit is gone (except for the Missile Turret because humans are smart), and all the air-to-surface stuff took steroids. If you wanna fight stuff in the air, you better be in the air. And that's a problem Blizzard needs to carefully consider.
4. The fucking Banelings. Just require a god damn Lair before Zerg can produce a Baneling Nest. Speedlings rape Marines. That's covered. Roaches (lol) should rape Zealots. That's taken care of. Speedlings rape Stalkers. Done. Sentries aren't a big a deal. Speedlings rape Marauders. Reapers should be removed. Let's rebalance Tier 1 Zerg without the fucking rolly pollies. The fucking Baneling is like 10:1 efficient against marines, coupled with the fact that Speedlings already rape Marines, I think this is a little overkill.
Other problems: the Void Ray, the Siege Tank, Zerg sucks, and I'm addicted to SC2.
Edit: Other problems (extended): The Ultra-lol (being addressed, apparently). Zerg not only sucks but is boring. Zerg has one effective spellcaster (being addressed, apparently).