"Power tends to corrupt." If this is true, then democracy may well be the maximin solution. But is it true? The word "autocrat" makes people think of Hitler and Stalin. They don't think of Frederick the Great or Deng Xiaoping.
Power often corrupts, but not always.
1. When power is insecure, it is dangerous, like a cornered wild animal: totalitarian spying against potential conspirators, suppression of dissent, brutal retaliation against political opponents. Secure power has less need for such behaviour. As Bismark said of the press "they can say what they want, and I will do what I want".
2. When power is a "family business", the leader's time preferences change and they want to ensure they pass a prosperous country onto their children. That's why old-school monarchs, for all their faults, were less rapacious than third-world dictators - the dictators knew their time in power was limited, so they made out like bandits while they could.
3. Many people are actually quite nice and will use their power to help their fellow men (or at the very list, fellow countrymen).
Consider that Communist China has transitioned from Maoist schizo-state to pragmatic autocratism and now to some kind of quasi-democracy, all without major revolutions. I see the real danger of technocracy being Brezhnevism, not Stalinism, but the same thing has happened with modern day democracy. (The current "democratic" system is designed to prevent charismatic populist politicians (ie, potential Hitlers and Stalins) from making much significant difference - how much personal impact over government policy did Bush have, for example? Or, for that matter, Obama? - and instead most power rests with hundreds of unelected but government-funded agencies.)
"So the best government isn't one that is not subject to control by any political interest, because objectivity and neutrality in politics are never going to be anything more than daydream. Rather, I think the best government is one that is open to control by so many conflicting interests in so many different ways that the vectors eventually balance one another out. Politics is meant to be dull, boring, and utterly predictable. Because when politics gets exciting, people die! It's OK when it's your own life, but don't put others' lives and human rights in peril."
I definitely agree with your last 3 sentences. The thing is any kind of true democracy is going to be full of exciting politics. Your ideal of a system where the vectors balance out is savvy (were you a British colonial administrator in a previous life?) and is also quite close to the current system. Designing a government that is ineffective by design is a good way to prevent tyranny. Unfortunately, it also makes it unable to make difficult-but-necessary decisions. Example: who in the USG actually has the power to reduce the deficit? Will this situation change in the next 20 years?