If you have one AI slot filled for a character and the other AI slot empty, they'll still alternate between slots in whatever order you set (random, round robin, etc...). If a slot is empty, the character will autoattack. So, if you only have one AI routine per character, and you want a character to burn through their routine more quickly, assign the AI to both slots.
(I could use confirmation on this behavior- I reproduced it on Pallegina as a Paladin + Fighter but I'd like to be sure.)
Does anyone know what "Best current threat" means? Threat to who: the character using the script, or threat in general on the field?
"Best current threat" is an ambiguous description to begin with. I assume it means the strongest enemy on the battlefield, but even then, how it determines that would be a total mystery.
I'm not sure, but I've been setting "Most Damage Done" as the target priority and that's how I've been identifying The Big Bad.