My position to all this balancing stuff may come from the fact that I don't play online, only onlan and I've of course played games where very different starting conditions had an effect on the early game but I've not detected a rule that this always leads to defeat.
Of course skill differences between players can overcome map layout differences. However, there comes a point where the player skill difference needs to be significant simply to overcome the map's inherent bias. If, by some fluke, you do end up in a scenario where you're playing against an opponent of such significantly different skill and the map happens to arrange itself in a layout that neutralizes this skill difference, it might be somewhat interesting (the equivalent of a handicap). However, this is a rarity. More common is that someone has a disadvantaged start location and gets crushed as a result.
The AI is much more forgiving than an experienced player in multiplayer. In fact, it's really not even comparable. There is a certain evolutionary factor in multiplayer gaming, that players learn and acquire new techniques from superior opponents they encounter. Those who fail to acquire these techniques successfully usually leave the online community because they simply cannot win against those who do acquire those techniques (mastery is another thing entirely...). The result is that everyone who is left is quite solid and competent, usually being well rounded players and quite vicious. There is still a wide range in skill, but the difference in skill is more subtle than you would expect, so even slight variations in game mechanics and balance have a massive reprocussion.
I agree with you as long as we are talking about small maps. The larger the map the less the influence of early games struggles due to bad starting conditions in mid to late game because on larger map you simply have more options for expansion.
This is true to an extent, but significantly advantaged mid-game positions are quite rare. Moreover, a strong early game position means you're able to expand faster and more effectively in the mid-game. If the map is very large, then I can start to agree with you, but I'm not aware of any 1v1 map that's anywhere near that big. Even on medium-sized maps it's hard to recover from a bad start, because the enemy will be one step ahead of you every step of the way.
Team games tend to even out, because the chances that everyone on a team is significantly disadvantaged or advantaged are slim. That said, I've lost several allies in games where they begin isolated and easy prey to a two-pronged rush. Sometimes you can't help these matters.
I've been playing RTS for very many years and in the early game phase of most games you have to play an optimized build order as fast as you can. One wrong click or a few mph slower than your opponent gives you a big disadvantage in late game.
There are some games (Age of Empires series being a blatant example) where you do need to spend a lot of work getting the timing for your economy down pat in order to be competitive. Sins isn't nearly on the same level as AoE in that regard, and furthermore it is actually quite lenient in terms of economic micromanagement. It's not so much about getting things done fast as knowing how to spend your resources to balance economic growth and research.
