Perhaps the spells will show you more damage, but I'm not sure. But your stats will tell you that your int value will give lower additional damage for every level and that every additional point of int is just like a drop on a hot stone. If this is intentional, I would rank it as one of the worst ideas ever.
It like Wits telling you, that every point of Wits only gives you 0.3% at level 8.
So:
Level 6, Int 23 (4%), Geomancer 1: Fossil Strike 57-70 damage
Level 8, Int 27 (2%), Geomancer 1: Fossil Strike 87-107 damage
Estimation if Points put in Const instead of Int:
Level 8, Int 23 (-6%), Geomancer 1: Fossil Strike 80-99 damage & +88 HP
