I don't think intelligence should increase spells effects.
Because Strength doesn't increase warrior abilities effects (stun, rush, whirlwind, etc...)
Because Dexterity doesn't increase ranger abilities effects (multishots, etc...)
So right now it's well balanced : nothing do nothing.
But :
- Strength improve melee hit and carry score.
- Dexterity improve ranged hit (dexterity is the worst stat in this game, really useless. It should improve something else (ranged hit and something else), and it needs it more than intelligence).
- Intelligence improve skills points per level (but only each 5 points).
So to balance Intelligence you don't need to improve spell (as Strength and dexterity) you only need to create a system with "half-skills points" and reward by skills points when you decide to improve intelligence.
