I think the biggest thing skills need is a higher level cost for higher level spells. So fireball would take 2 or 3 pyro or else it would cost more ap to use. This would be an easy way to give more meaningful decision to your choices without as much need for it to be as balanced, unlike now where they all give only stats for leveling them up.
That would be one effect that could be added to skills, yes.
But not the only thing effect skills should have. I think it would be better if skills would have several such relatively smaller effects, which attributes would give bonuses to.
