I don't agree that the AI is exempt from range rules or ignores fog of war.
Lol... Based on what proof? Sorry, but I trust a forum poster with evidence (tests, screenshots) about a million times more than I trust a dev with a simple one-line denial.
I will say that providing a fun opponent to beat is the primary objective of AI, and the AI gets handicapped in a lot of cases where it would be more competitive, just because it would make the game less fun (handicapping expansion, allowing diplomacy where war would be better for the AI player, etc).
This should be entirely based on the personality of each race's leader, when played by the AI. There is extensive XML to define leader personalities in Civilization 4 for example, with biases toward war or peace, how often and aggressively they attempt to build Wonders, etc. I would have done it exactly the same way here without a second thought, personally. The build priorities lists in GC3's leader XML are admittedly somewhat similar, but much less detailed and they don't cover warmongering at all.
But PalaceGuardian is right that we do review winning strategies and balance accordingly. The primary goal of that isn't to make the AI seem more challenging, but to make sure that the game is in balance with itself. Otherwise the game becomes a one trick pony where money and research doesn't matter, only building one particular influence improvement. Or carefully optimizing your fleets don't matter because there is one missile launcher that is hands down better than everything else.
I like this a lot, and totally agree with it. I do feel I have plenty to complain about when it comes to this game sadly, but this is not part of it.
With a game as big as GC3, that balancing goes on forever. You would be amazed at the difference a +1 to much can make in the wrong place.
This depends entirely on who is doing it, imo. Balancing is a skill, requiring a combination of, in order of importance: excellent intuition, extensive game knowledge and experience, dogged persistence with data/testing/spreadsheets, and a bit of cleverness. As someone who has worked on Civ4 for 11+ years and feels he's pretty darn good with all of the above, I feel like you're exaggerating and over-generalizing with that statement, however with average developers I suppose I must concede it's probably spot-on.