Unlike traditional party RPGs, this one works better if they all do one type of damage. Substitute a ranger who specializes in bow for one of the spellcasters, make your mage be a summoner who also heals (water-based, I think).
By stripping away physical armor, you can actually start hurting enemies faster.
As for killing yourself with your own spells.... I don't know what to say about that. Turn off the party AI and control them.
