Excelsior

When a spellcaster pet is guarding you and it attacks a mob that aggroed you the pet doens't cast spells.

However the pet casts if, while guarding you, it defends itself from a direct attacker.

If you send the pets against a target with the "kill" command they do cast.

Pets have no problem throwing fireballs - in defensive, aggressive or guarding mode.

How to reproduce.

1. take a spellcaster pet
2. say "all guard"
3. find an aggressive monster and wait until it targets you.

The pet will react but it will not cast spells

I checked this with:

dragon, mule, nightmare, summoned fire elemental, summoned demon, wyrmy wyrm, energy wyrm, fire wyrm

The only pet that I have seen throwing a cool blue kinda of fireball is the noble, doesn't happen often but I have seen it whether is guarding you or you send them to kill. All other pets that you mentioned in the list I have no idea cause I haven't use those pets to fight... well with the exception of the mule and that one doesn't throw anything.

If your post is about spellcasters pets that 'should' cast spell as special and now they aren't then probably you are right as some or all are custom in UOEX. Have fun!