I see the word, "balance" being thrown around a lot on this forum, and it infuriates me when I see people attributing a balance issue to a design flaw.
I hope to clear up the difference between the two, as well as give some examples of each.
In the gaming world, when we refer to something as balanced, we would suggest that the metrics used to compare the overall objective of the game will result in an even (50/50) distribution of wins and losses. In the case of Starcraft, we use the 'win-rate' metric as the objective (since winning is the primary objective in a regular match).
If we notice that a particular matchup has a statistically significant deviation from 50/50 (larger than +/- 5%), then we can say that the matchup is favoured to one particular race, and that it is imbalanced.
While this seems to be the rudimentary problem, it is not the same as design, which is what many people refer to when they claim 'imbalance'
When we refer to design in the game, we refer to the overall plan set forth by the developers for each race, map, unit, etc. The idea of asymmetric strengths actually refers to racial design. A race that is strong at one point in the game, but weaker at another point represents difference in design, not imbalance.
What's important to realize is that Design and Balance are tied to each other, as changes to the design of a race can potentially result in imbalance.
The Gold standard of examples: Late era WoL PvZ
For all intents and purposes, the era of BL/Infestor was balanced.
BL/Infestor was found to be extremely powerful; Z started skewing the even distribution to their favour when they could reach the late game. In response, Protoss popularized 2 base all-ins to prevent Z from reach the end game (Sentry/Immortal).
Both BL/Infestor and Sentry/Immortal had winrates above 50%. However, the distribution of wins and losses (the end goal of each match) resulted to roughly 50%. The matchup was indeed balanced, as David Kim has always claimed.
However, in terms of design, this matchup was a mess. It was not fun to play against, it was boring to watch, and it resulted in stalemates and repetitive play over and over again. If Zerg didn't stop toss from 2 base all-inning in the early game, or; if Protoss was unsuccessful in the mid-game to stop zerg from getting to late game, then the opposing team tended to roll them over with either Sentry/Immortal or BL/Infestor.
But was it balanced? Winrates say Yes.
Was it fun? Hell no.
Was it designed well? Hell no.
The Current situation: HotS TvP
We're now in a similar situation in HotS TvP, where the design of toss changed to a point that frustrates Terran players.
Statistically, the matchup is balanced. David Kim balances what he is given by the design team. 52% is not statistically significant enough to indicate a sort of constant imbalance.
However, the same questions can be asked as before:
Is current TvP fun? Not really, no. Constantly being aggressed for little to no pay off until late in the game is difficult to manage. Trying to go on the offensive is more difficult due to design constraints.
Is current TvP designed well? Well, even from the get go, TvP has always been a blemish in the eyes of the community. The contrasting differences in playstyle has always been a target for players. From the strength, mobility and, consequently, fragility of infantry units, to the weak, relatively immobile, but powerful gateway units, up to hard counter after hard counter on each side, the matchup tends to play out in a very hectic playstyle.
But is it balanced? It most certainly is balanced. Winrates suggest quite clearly that terran wins just about as often as toss.
Starcraft 2 is most certainly balanced. However, the flaw in its design for each race can make for a very frustrating play experience. Just try to keep in mind when you are frustrated with a string of losses, that, somewhere else on battle.net, a player of the race that just beat you is getting their ass handed to them by someone of your race.
Try to remember that it is, after all, just a game, and that if you do not enjoy what you are doing, you are not required to play. You can take a break, come back to it if you really want; and if not, well, that's okay too.
Just try to remember that the issue is design flaws more often than not, as the balance team is doing a great job with what they have. Also, mindless 'Protoss IMBA' or 'Oracles OP' with nothing else will not improve a game, or a community. It just dilutes down the voices of those that have the potential to improve the game.
If you've made it this far, thanks.