I don't think "Guides" where the AI follow a precise trait plan is a good idea, but it should use some logic picking traits.
Ceresa should NOT go anything but mage.
Warlord Verga should go assassin or warrior.
Its simple, the system should pick the path in which the hero is already strong, if the hero have few HP, or access to fire magic (and normal hp, and no bonuses to other stuff) it should go mage.
If the Hero have decent HP, and Decent initiative, go for warrior.
If the Hero have nice dodge and damage bonus, go for assassin.
If the hero have the weak trait, or clumsy, or -30 accuracy to high lvl mobs trait, level the hero to 4-5 with assistance and go path of the governor.
Stuff like that would help the AI not picking path of the warrior for weak heroes, or path of the assassin for oracle Ceresa, or actually playing Queen Porcupine. (Ok I just don't like her build ATM).
and it cant be improved just with priorities because fireball IS a good spell but ai need to full build to cast fireball or build elseway and dont cast it at all, even if it could
That's not a good rule, my current hero have the Porcupine's crown, and I enchanted my hero with the ability to throw fireballs, just 1 battle ago I bashed some wolves, even though my hero is an assassin, but it should ONLY cast fireballs against big groups!
(The wolf stack was 3 big wolf stacks with the dire-wolf buff, so they all had +7 attack, I decided to just blast them and be done with it).
Sincerely
~ Kongdej