Some things I noticed on the very recent AI:
1) AI struggels if it can't get straight to the city if it wants to attack.
For example, the AI needs to pass my Fort which isn't directly on their way:
W W W W
1 L L L 2
W W F W
(W=Water, L=Land, F=Fort)
If the AI wants to walk from 1 to 2, they need to conquer my Fort because of it's ZoC. (I know it's poorly illustrated, but Koshling knows what I mean, he as my Savegame and is working on it)
2a) AI won't use Ships to get over a small water area if departure and arrival is at the same continent. Imagine the small area of water between Spain and Africa. If The AI in North Africa want to conquer a city in Spain, they would walk all the way, Over Egypt, Suez, East Europe, the Alpes, France... Even if they HAVE enough ships.
2b) That is a problem but it gets even worse: Imagine on Suez would be an active Volcano so there is no way to walk this way! The Player would easily use ships to pass the volcano, but the AI just keeps sitting in Africa.
2c) And I think that's the same as 2a and 2b: The AI can't use land-transports or, if they want to go from India to Korea, ships, eventhough ships have 3 or more movement and their troops only 1.
3a) AI uses Forts to connect resources, even on their own territory, which is great. But it doesn't defend them properly (if at all) even if they see my large army nearby. It's very easy to conquer those forts so they haven't access to the resource anymore - and can't get it back so fast because
I know that I need to defend my forts.
3b) AI rarely uses forts to secure their boarders. Especially small landbridges are so much easier to defend when you have a fort. And, I don't know if it's possible, but since you have a SoC it should work: They never use Forts to secure resources outside of their boarders.
4) There are weird things going on with the odds...
a) Wenn I attack with my Hero Sargon, he has 100% victory chance. When I attack with any other hero, they have ~40% chance. He can't be THAT much stronger? (Savegame is following)
b) My chances of attacking with my hero are around 95%, but when I surround the city with ballista elefants, the chances for my here are only 5% ?! (Also, Savegame is coming later)
c) Even though they say the victory chances for my Praetorians are ~90%, 2/3 of them die (n=15). This MIGHT be bad luck, but could also be wrong displayed. May have a Savegame, but it is probably reproducable with the two others since they were all at the same siege within a few turns.
5) Same savegames as 4) -> My stack is sitting on a hill next to a city, and they have some many units that they could easy kill me. They might lose a lot of units, but they should be able to kill my entire stack - leaving my empire mostly undefended, except for a few Town Watchman.
6) The AI doen't use SoD. I know you know that, Koshling, and I know why the AI can't do it, I just want to mention it here so it won't be forgotten.
7) The AI doesn't know when it can use the size of their stack even with low individual odds. IE If you have 10 Defenders and the AI has 50% chance to win, it doesn't matter for the AI if it has 10 or 1000 units.
8) As far as I can tell, the AI does not plan ahead when going to war. If I have a city in the far north (or in a desert), they go for it with a giant stack, but since they get so much terrain damage, they retreat without even attacking. If I plan to conquer an ice/desert city, I use either desert/ice combat promotions, the march promotion + a healer or I build a fort near my target city where my troops can heal.
Note: This might be fixed now. I never play with terrain damage on since I saw that, because it really cripples the AI. A city with a decent deense (like 5 Riflemen and a Wall) can easily be defended just a few tiles away from my enemies boarders and be an excellent Airbase.
I don't have a savegame now, but it can be easily provided if you need it, just let me know!
9) When my "Friend" moves a big stack of units through my territory, I build a large stack of well promoted Bandit Riders or anything else with hidden nationality and beat the s**t out of their stack. This way I get GG Points, Slaves and I know, the AI will use the stack against ME later anyway -.- It would be very sneaky if the AI (on higher difficulties) would do this, IF it knows it doesn't need your support against their enemies and/or if they wants to attack you later.
10) Sometimes it is wiser to leave your city and let the enemy conquer it. Especally if you have mostly units designed to city attack. Would be another thing that would the AI on higher difficulties makes smarter, not better by giving it more bonus.
11) I have no idea why, but the AI seems to have their primary stacks nowhere near the Boarder. In my game, the Zulu control the complete african continent. There is no "neutral" or barbarian territory there. I am the only threat for them, near the suez cannel. But their stack is just not there.
-> The AI should keep their stacks near the boarders so they can counterattack quickly. Maybe not in my visible range, so they can suprise me.
That's all from the top of my head now, I'll let you know once I find something else.
And if you need savegames for something, I'll try to get them, making up a situation with the WB if necessary
Just let me know!