I have Xoti setup to cast Interdiction at the start of a fight. I noticed that she'll only do it if I set her to Aggressive or Defensive but not if she's set to Defend Self. Why is that? Is she not yet considered "in combat" so she does nothing until an enemy attacks her?

Also, is the difference between Aggressive and Defensive the range in which a character will seek out an enemy to attack? I assume if I set her to Defensive she'll only seek out an enemy to attack if the enemy comes close enough while Aggressive will attack regardless of how far away the enemy is.

I think the difference between the Aggressive and Defensive is the range.

 

In Pillars of Eternity I found that Aggressive was too aggressive. My characters ran to attack monsters that were too far. So I set them to Defensive. With POE II Aggressive seems to be working OK but Defensive setting is too passive. So now I set all my characters to Aggressive.

It seems the developers just try to find some reasonable values for these settings, maybe they are even experimenting a bit. I doubt this is documented somewhere.

"Defend self" only triggers once the person is attacked. I use is when I want my tank to block a doorway without moving, yet engaging enemies that attacks him in melee.