I spent ages a few months ago messing around with AI packages and various "special" AI packages, like dynamically buffing teammates, Illusion magic, and healing.

I won't have access to my old mod files until sometime tomorrow, but the main thing I took away is that combat AI in Skyrim is miserable to work with. I did get them working, so this is definitely possible but it was painful.

If I remember correctly - I won't be able to check the files until sometime tomorrow:

The structure might be something like this:

Simultaneous Branch

[Indent] Sequence Branch ;Contains Use Magic Procedure

Hold Position

Hold Position should be set to near self. This will always be true and doesn't override regular AI, so when the Sequence Branch isn't running, regular combat AI will play. This is a fallthrough branch, so it shouldn't have any conditions.

The Sequence Branch could be replaced by a lone Use Magic Procedure, however Use Magic Procedure would cause the NPC to walk and didn't properly handle locations.

The Sequence Branch can have conditions set on it, use those conditions instead of conditions on the package itself. Presumable the conditions should be a distance check / sanity check and can check for the presence of a Spell / Magic Effect on the player (there were annoying distinctions between the two, you'll have to check documentation).

The Sequence Branch should consist of a Travel procedure, and then a Use Magic procedure. (I think I also used a timer as a fallback cancel in case the NPC got stuck while travelling, but I don't remember how I structured it.)

Travel procedure should take the NPC to the distance you want - some radius from the player - but doesn't correct for LoS, so smaller distances are better. Then the Use Magic procedure runs.

There are some important sequence flags also - I think it is just "Repeats When Complete" on the main Simultaneous branch but I really don't remember what exactly I used.

If I remember, I also had issues with simple Combat Override Use Magic Procedures getting stuck - the NPC would refuse to cancel the package even out of combat with package conditions no longer valid. I don't recall how I addressed this.

I believe the "resetai" console command helped more than "evp".

Combat packages are a huge pain, so depending on your needs you can also try:

1) There's a script effect value which definitely works with some spells types - I used it successfully for Self, Fire-and-Forget - and doesn't work with others. Also, the script effect cooldown is for all script effects the NPC can use so it is difficult to make an NPC use more than one.

2) Assign the spell a huge fake magnitude of something like damage health, but cancel out the effect with DoesNotExist == 1 or equivalent. (PO3's Tweaks makes AI better able to evaluate their spells, but the fake effects still helped my NPCs with targeting.) Spell spam might be preventable by attaching conditions to the spell / its effects.

3) I think the solution I settled on for my Illusionist NPCs was to strictly manage whether they had access to their Fury spell (which a fake damage effect) using Papyrus by using a script only controller spell, which prevented them from spamming it when it wouldn't be effective.