In two king games I've lost one city. First game was incredibly peaceful with a single war in which I was DOW'd by an overstretched Mongolia. Second game the DOW came from Greece, and I blocked their access to the rest of the continent. He brought everything he had and took my city with ease and had me concerned for my capitol. Haven't had that happen to me on King for a long time.
Back on the city attack AI, I've run into another issue - nothing's been done about the AI's city prioritisation. While I understand from the patch notes that the AI now has a different system for selecting target cities, it still fixes on one target and isn't able to adapt, and it takes no account of defensibility. Take my current game:
On the couple of occasions he's been on the offensive, Kamehameha has only tried to attack Barcelona, which is basically impossible to seize pre-air power due to the rough terrain and limited area to attack from the sea (and that's before I dropped the Citadel, a new feature in the last few turns). He's landed occasional units (including an oddly aggressive settler - I've seen this a few times recently) next to Cordoba, but only as an attempt to move on Barcelona; however Cordoba itself protects Barcelona from attack. Cordoba is also flatland with an extended shoreline, a much better prospect for Polynesian assault.
Something should be done to let the AI calculate when an attack on a city is not cost-effective (maybe units lost vs. units killed in the city radius? In fact in this entire war I've lost only one unit, and that was during an exploratory attack on Samoa), whereupon it should look for other targets that might meet its objective. Cordoba might not be the city it wants, but if it can take it, it will be in a position to surround and isolate Barcelona at the very least; alternatively it could move directly on Spanish core territory and simply ignore the Barcelona bottleneck.
This lack of adaptability is crippling, particularly when the AI has an objective so strong (as in this case, its apparent need to break out of its corner of the continent) that it refuses to negotiate peace even when losing and even when its former ally (Attila) (a) declared war but, being nowhere near me and having no interest in my territory, never actually got round to attacking, (b) randomly sued for peace by giving me large amounts of money, (c) declared war on Kammy for a brief period.
The only reason Polynesia's still in the game (or at least that Samoa is) is that I haven't yet got round to building a fleet, the best way to take out Samoa. Its isolation works against Polynesia - he won't have allies in a position to attack, and away from Barcelona he's hemmed in by Alex (who also blocks the Huns from my territory). Alex is the weakest AI I've met by some way (and based on tech demographics, probably the weakest in the game), but I do have a DoF with him that makes him a useful buffer.