Okay but you read this:This has nothing to do with AI's battle performance. That's another subject needs to be fixed. This is about how are armies programmed to behave in the campaign map. They might not wanna fight my army because of strength comparison but this doesn't mean they should ignore it and go for a kamikaze attack. There is literally no reason to justify this nonsense.
They do not have any option to do other things. They only know if they have more or less power for auto calc battle. They could improve the game by making the AI have more options and not depend on just checking power (this is also how they choose siege targets) but there's zero indication in 3 years that TW wants to move away from this simple AI. Their main concern has been trying to make the map not paint itself too fast while the player is farting around.They must siege or raid or attack a smaller powered party. They can't pull in all their armies and parties to gang up on you proactively.