While it's definitely true that most beta testers are powergamers, I most certainly am not. I played the beta on Easy most of the way through (switching from Normal shortly after the demo portion) and I can assure you, the game is definitely winnable on Easy. As others have said, the difficulty got turned WAY down from the early versions, and easy is now actually easy.
My troubles occurred in not putting enough points into Endurance early, and looking at my build later, I wish I would have skipped the one human I did keep and made him a slith. Since you've edited your Endurance, you should be better there. I also have to second the advice to split your magic/priest spells up. Once I started having my mage learn priest spells and my priest learn mage spells, life got a lot better. Two healers and two fireblasts are better than one! Since you're having a lot of trouble with mental attacks, be sure your mage gets Unshackle Mind.
Also, don't forget about those priestly buffs. Sure it takes a round away that he could be hammering away at the baddie, but the lessened damage you'll take is worth it. Try to buff up before you hit the actual enemy, most of the enemy encounters are obvious enough that you'll have plenty of time to throw on at least a couple buffs plus a haste spell and be golden.