The big problem with the IQ 13+ spells is the high fatigue cost for the effectiveness.
The advantages for an IQ 13 wizard are:
- Staff III (the good staff spell, turn your DX 11 into a 14)
- Cast one-hex Illusion silently
- Scrying (but success is unlikely)
- Flight, Summon Gargoyle, and Telekinesis are all expensive, but useful for a lift. (Just know a hero who is a climber.)