I actually think that bug (if it's a bug) is quite good. Otherwise the multiple misc slots on certain pretenders are next to useless. Ok, misc slots rock on combatants but most creatures with more than 2 are caster types.
Spell Focus, Amulet of Luck, Amulet of Missile Protection, perhaps Eye of Aiming, Girdle of Might/Amulet of Reinvigoration, Amulet of Antimagic... There are many good items that benefit all mages. It's just that the OFFENSIVE items are much more rare.