Change to qauke spell idea
Why not make quake, a flat number of damage, rather then a %.
With each lv research it increases it bonus multiplier to walls and Max damage
And increase cost of the spell over all, or reduce radius of impact
Example
Lv1 200 damage, x2 wall damage
Lv2 300 damage, x2 wall damage
Lv3 400 damage, x3 wall damage
Lv 4 500 damage, x3 wall damage
Lv 5 600 damage, x4 wall damage
Thought , suggestion. Numbers are just example, later I'll sit down and look at current wall hp and base something off of that