Entire system with 3-5 skills that just add +10% to damage is stupid.
Why we cant have something interesting, like metamagic?
Yes yes, lets switch element of some spell, if hero have both fire and lightning, special spells can be unloked, like ball lightning or searing ray, if special skill also unlocked.
Overcharge, usefull, require magic staff to use, 2x damage (effect) at cost of 3x mana.
Bending\breaking rules skills, that allow to hit with magic othervice spell immune creatures.
Silent cast, ignoring silenced condition, enemy (player) wont know what spell is casting, at some mana or time cost.
Instant cast, cast spell right now, but with decreased stats (usefull alternative to -1 turn to cast already exists).
Such skills will be interesting and will provide new tactical options, not just add damage to spells already here.
Also caster level+x will be exceptionally usefull as both feat and skill.
Magnar can use level+3 as replacement to 50% damage, thiw will help a lot.