Fire mages casting Rage on Umbrals

[FAJ]

I am curious as to how the AI chooses its spells when it is disregarding scripting.

Recently I had a friendly neighbor suicide some militia an event gave him to kill them off. I had 3 diseased warlocks in the province, with slaves, scripted to "blood heal" then stay behind troops. The idea being to heal them back to full and keep them blood hunting for another 10 turns, in which I would blood heal them again, doing my best to retain utility out of diseased hunters untill they get eventually feeble-minded. Each was at HP < 40%

Instead of blood healing, they spammed "body ethereal" on their own blood slaves. and after they were all ethereal, they cast luck.

Is it possible that with old age, comes senile behavior? These warlocks are sacrificing themselves to buff their slaves!