Combat magic not being mitigated by armor is a big plus, but none of it scales at all.
And there it is. One of the biggest mechanical problems with magic. It doesn't scale. Equipment does.
Why is this bad?
For example +4 healing may be excellent in the start of the game (on lower difficulty) but later on it's absolutely useless.
With scaling based on int:
Heal at level 1:
Heals the target for 25% of the casters total intellect.
this means (with 16 int) a heal of 4 at level 1.
Heal cast by a member of your dynasty at high level:
Heals target for 25% of the casters total intellect.
this means (with 100 int) a heal of 25.
Scale and balance. It also means your stats actually have an effect on your spell casting like strength does on you melee. Ignoring the one caveat in arcane arrow.
You could then further extend this with research and say for example you get a bonus multiplier for every level of spells you research, say +1% as an arbitrary number.
Level 1 - no bonus to casts.
Level 2 - 1% bonus to casts (heal does 26% of your intellect)
Level 12 - 12% bonus to casts (heal does 37% of your intellect)