A modder by the name of ZiggiBoy101 fixed that issue where the AI go up siege towers in groups of like 3-4.
He describes what he did in detail right here in the mod's description:
Given that the game has been out for like an eternity and sieges are still broken, maybe ask if you can cheat off his homework and fix this in vanilla?
He describes what he did in detail right here in the mod's description:
SiegeTowerFix (Discontinued)
This mod fixes the issues there is with AI trying to find their way up the siege towers
www.nexusmods.com
Given that the game has been out for like an eternity and sieges are still broken, maybe ask if you can cheat off his homework and fix this in vanilla?