About melee and ranged characters, I have always invested everything in DEXterity, since I have noticed that monsters may have an amazing armor class and it is useless to have a greater damage capacity if you can't hit your foe (lol, it looks like Goku talking to Gohan in Dragonball, while training to fight Cell!

Also, I'm having a bad time against enemy spellcasters: I'm not sure that they need to "hit" my party to deal damage, but having more HPs looks even more important as I proceed further in the game. But HPs are increased with STRength and ARMor, so I'm beginning to re-evaluate the important for the first one.
I was also wondering if improving the mage's DEXterity may have any meaning, since it is only used to hit with any weapon but the mage doesn't use them.
Also, does have any utility to equip the mage with any item that increases the DAMAGE? Like rings? Does it increase the damage dealt by his spells?