so, I just started playing Civ 5 again... idk if it's the patch or if it's always been like this, but goddamn the AI is annoying.
even with domination victory turned off, they war incessantly.
I recently did an 8-civ game on continents... it was me (India), Russia, England, Mongolia, and Japan on one continent and Persia (I think), Germany, and China on the other.
by the renaissance era, China and Germany destroyed Persia while on the other continent, England/Russia/Japan all ganged up on Mongolia, after which Japan took out England and then engaged in 500 years of war with Russia before finally killing them in the industrial era.
both Russia/Japan declared war on me at various points, but purely defensive wars are pretty easy to win (wipe out invading army, counter-attack by invading one of their cities once all their units are destroyed, and then make peace, regifting the city back to them)... I'm sure I was next on Japan's hitlist, but Russia kept them occupied for most of the game, allowing me to complete my culture victory in quiet (and with almost every hex of my border with Japan occupied by a unit)
every single game has been playing out like that, with only 2-3 Civ's left by the modern era unless I play on an archipelago map.
edit: and once I started building the Utopia Project, of course, China (the only Civ who was friendly with me in the first place) immediately went from Friendly to Guarded.