One thing I've discovered while playing that nobody else has mentioned yet is that eventually you're going to run into enemies that apply a "nullity" effect to you, which means your characters can't use disciplines and your spell casters can't cast spells. My mage and priest had been focusing on their spell casting abilities to the exclusion of all else, and when I ran into that effect, those 2 characters became suddenly useless in a fight. None of the potions, elixirs, or scrolls seem to remove the nullity effect. Even if they have some spell scrolls/wands in their inventory, those don't seem to be very effective (not as effective as spells). I don't remember seeing this nullity effect in the first Avernum game (Escape from the Pit), so it must be new to episode 2. So I wasn't prepared for it. I wish I had known, because I would have made sure the spell-casters had some kind of decent self-defense skills to fallback on.
At this point, I'm too far into the game to start over with new character builds (all my characters are level 32). And I'm a bit of a purist, so I'm not willing to use the character editor yet. To workaround it, I've done 2 things: 1) gotten combat training for them where I can (some trainers won't train me because the tank in my party is too skilled, and they say they have nothing they can teach me), and 2) stocked up on invulnerability potions and wands/scrolls for my spell-casters so they can survive a fight and at least contribute a little bit of support to my other characters.