I played 2 campaigns without WarAttrition mod that went at least over 4 in-game years and 2 with the WarAttrition mod. What I've seen is:
1. Long term games seem to generally become a Western vs Eastern Superpower; with Vlandia & Battania being the prospective Western powers and the Khuzait, Southern Empires being the prospective Eastern powers in order of likelihood. It is also possible for a lone super power to form on the map before a rival and they just rock the world.
2. In all the games the Battanians looked like an early powerhouse but also in pretty much every game they seemed to become over extended and get worn down fighting on all sides overtime and then the Vlandians slowly became THE power on the western side of the map. The Vlandians have a penchant for keeping the core well trained army they start with intact better than the Battanians and with their backs to the sea slowly build momentum and stockpile of quality cavalry. It is possible for the Battanians to snowball to be the dominant one but I believe that requires they have a LOT of success early on and that they also cripple the Vlandians rather early as well. Time is on the Vlandians side.
At least from my games I don't see how the Western Empire survives. They seem to almost always be the faction that takes the most damage the quickest. But I suppose if somehow Vlandia and Battania didn't become the Western superpower the Western Empire is the 3rd most likely.
3. In the East the Khuzait seem the prime candidates to become a superpower. Like the Vlandians they don't necessarily explode right from the get go but steadily build up. They, like the Vlandians, are positioned well to prey on both of the weakest factions, the Sturgians and Aserai, and have their backs to the edge of the map while doing so. The Southern Empire is the 2nd most likely to become the dominant power; it is well positioned to prey on the Aserai while not being as surrounded and exposed and the Western and Northern Empires. But in big question in the East is, "will the Kuhzait Horde be stopped?"
4. The Northern Empire is something of a wild card. They occupy the most overall central positions on the map, border most factions, are but a small distance from the Vlandians, and are far really only far from the Aserai. They generally seem very stable early on as they start out with, i believe, the strongest imperial army. But their central location makes them prone to getting worn down by fighting on all sides like the Battanians and what happens to them in the mid to long term seems much less predictable than most factions and will have a huge impact on the overall balance of the world. I feel like the Northern Empire, and the Battanians, are the two factions whose fate is most unpredictable and I don't think it is a coincidence they are also the most surrounded factions.
5. In almost all the games Sturgians lost wars early on to either Vlandians or Empire factions and never seemed to really recover in terms of troop numbers. The Sturgians seem weak and fragile to begin with and completely unable to contend once they lose a single city. In 2 games Tyal was also lost to Khuzait pretty early also so they were getting boned by Imperials/Vlandians/Battanians and Khuzait from both directions. In once game with the WarAttrition mod the Sturgians at least stuck around a bit and didn't get wiped off the map too fast but they seem to always be the weakest faction barring some other faction have terrible luck something like getting all its armies wiped out while at war with 2 strong factions.
6. Aserai also followed a similar trajectory in all the games. They seemed to lose against the other factions almost as badly as the Sturgians early on but they are far less fragile and seem hold out for a very long time very stubbornly after the initial loss of a city or two where as the Sturgian's would go down like a house of cards. Even if they are generally the 2nd weakest faction they are usually one of the last to get wiped out in my experience.
Another thing I'd point out is actually how the balance of power between 2 kingdoms can be decided almost permanently by a large single battle. Once one side loses all its trained troops and has nothing but recruits against an enemy with a core trained army intact the wars become very one sided even if it shows overall similar troops numbers. Half the troop number or more are city/castle militia anyway.
On one hand I think it is realistic and cool but as things are the damage is far too permanent. Unlike the player AI seems to especially struggle with regaining a capable army once they lose the one they started with and it both contributes to the faction snowballing and makes repeated wars with factions very boring. After 2 wars with a faction I know I've wiped out any troops they have of worth I know they will pretty much never have an army of that caliber again even if the next time I fight them is years later. And slaughtering recruits and peasants with my army of tier 5 and 6 soldiers gets pretty boring. It stops feeling like epic battles and more like I'm mowing the lawn.
My most recent play through is very interesting in how it highlights this. I have the WarAttrition mod and have also played specifically to try and balance the factions on the campaign map. Bashing the armies of the strong factions like Khuzait, Vlandians, Battanians, Southern Empire, and Northern Empire while being a merc for the different weak factions, Sturgians, Western Empire, and Aserai who had gotten bashed.
The result has brought the AI's inability to recruit and regain decent quality armies into focus. Every kingdom is reasonably intact and has land and no faction has snowballed at all. But virtually every faction has had their armies annihilated also als troops numbers are very low with the largest faction having only 4300 troops. The Sturgians and Aserai, even with me kicking the tail of their enemies, seem completely incapable of rebuilding their strength. The Western Empire, like the stronger factions, has better luck regaining numbers but not troop quality.
Now in this playthrough all factions struggle to take any well garrisoned cities off each other because the troops counts for every faction is rather low. And the declining number of battles means less influence for the AI to even form armies large enough to take cities. It's 4 years in or so but probably the strongest army any of the AI factions could send at me would be around 800 strong of which at a minimum 60% would be raw recruits. As it stands with 2 fiefs I can support an army that would defeat any the AI kingdoms in the field and its 100% down to the AI being unable to actually rebuild a real army. That isn't fun to play to be honest and I'd prefer more of a challenge for the sake of long term being able to enjoy the same campaign instead if just becoming your tier 6s slaughtering tier 1 recruits in most battles after the first 3 or 4 years or so.
Ironically I set out to play in a way to counter act snow-balling and keep factions from dying since I thought that was what ruined campaigns only to find out everyone staying alive and everyone's armies being slaughtered so they can't take cities has ruined the game in a different way as it reveals the AI is very very poor as replacing armies and unable to keep up with the wearing down of the armies it starts out with.
