| This may not have been the best way to deal with them, but I finished TotL with a fighter/mage/thief and a bard, finding it nearly impossible to complete without spell buffs. The weaker characters you talk about, I assume they're spell casters, so you should probably make a monster wall or keep them a good distance away from combat, perhaps using the fling spell and run technique. If you have a strict healer character, sanctuary is perfect, as defensive and buff spells don't break it.
Tensor's, Blur, Mirror Image and Haste were my favorites. The Girdle of Ogre blood is a good item to provide five summons to take the enemies' attention off your party. Don't forget to haste your summons. It significantly increases their damage output.
If you have any thieves, the hit and run for backstab works wonders as well.
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