A higher focus on founding religions that aren't in the game, and a generally more aggressive religion founding policy. I often go through entire games where the only religions are RoK and FoL. Another thing is the terrible defense policy during the early game of the AI. They often leave only 1 unit to guard each city and only beef up the defense after the borders have settled down. This makes them especially vulnerable to raging barbarians and barbarians in general.
Maybe it's a good strategy to join an existing religion so as to get diplomatic bonuses.
The reason for that is that the AI isn't redding out resources it already has. It will accept fair deals if you offer resources it doesn't have... but the only way to find out about such resources is by trial and error.
Explanation:
http://forums.civfanatics.com/showthread.php?p=6019613#post6019613
http://forums.civfanatics.com/showthread.php?p=6019711#post6019711
Fix:
http://forums.civfanatics.com/showthread.php?t=246070
I think the AI is designed to spread its religion, as in the past I've held out from giving the Khazad Open Borders for a long time and the turn I eventually give in they flood my territory with tons of Thanes. I think the AI is building up Thanes just so it can spread RoK to everyone it can.
It's annoying and adds nothing to the game. The AI is as fair as ever when trading for resources it lacks, so it's clearly meant to still do fair deals. Just, thanks to a coding snafu which you can read about in my second link, the feature is broken and not working as intended.
Should Bhruic's Tradefix be used, the AI needs to be given an extra line to seek up to 3 of any Mana type. But more importantly (and needed even without Bhruic's fix), they need to assign a value to the extra Mana beyond the first.
If Resources which they already have are all granted a value in trade still, the AI is less likely to demand the overly unfair trades in general. The value should be based off: Buildings with cummulative bonuses (do not believe that we actually have any), Potential Trade Value (is the resource strategic & do I have good relations with someone who does not have the resource), Free Arcane Promotion (do I have 3 of the mana?)
AI city positioning is poor in general. I see far too many cities founded with a 1 tile gap to freshwater/coast putting them at a health disadvantage.
Should Bhruic's Tradefix be used, the AI needs to be given an extra line to seek up to 3 of any Mana type.
This tends to be a problem for gameplay, though. Any game with the Khazad or Luchuirp seems to result in all of the Evil civs converting to Runes of Kilmorph and becoming Neutral. The incentive to spread religions needs to be toned down, IMO, or at least for RoK. (An alternative would be to make RoK alignment-neutral like FoL.) This doesn't seem to be much of a problem in reverse with OO.
By contrast, Ashen Veil and the Order are almost always the last religions to be founded. There should be stronger incentives for the AI to go for them.
I saw many times entire stacks parked outside Acheron's city, unable to attack, but still standing there even during wartime. Could the AI be taught to take care of the little darling when it's ready to do it for real?