This was an issue in the original FFXII that I see still hasn't been fixed. The AI still casts a spell despite a mib being immune to it, over and over. For example, if I set up a Foe: Any > Slow gambit, the character will repeatedly cast it even if the mob is immune. However, if the spell successfully goes through, the AI knows not to cast it any longer. It's odd that the system can recognize weaknesses but not immunities. I would like to use the abilities in my arsenal without having to constantly manage each character. This needs to be patched.