But the dramatically powerful master skills (Storm, Arrow Storm, Meteor Shower, Hail Storm) all require 2-3 source, so you couldn't spam them all in a short span regardless.
You could very well spam those skills, because of Apotheosis and Graft skin scrolls. I one shot the final party on first turn, and one shot the final boss on first turn on my first play through.
I don't mean any critique by saying this. But from a personal perspective it felt underwhelming and ill-designed.