To add to the alternative firebolt nerf suggestions:
I'd like to see something similar to the catapult equation for firebolt. This fits with the diminishing returns Matrim suggested a few pages ago, and would also be a sort of "middle ground" between the quanta cap and the original formula.
Below is 1) the Catapult formula for comparison, 2) the original Firebolt formula, and 3) my proposed equation for the Firebolt card.
If we draw an imaginary line at the 50 point (quanta cap), the current Firebolt would deal 15 damage, whereas the new Firebolt would deal 16 (16.67, but rounded down like with the Catapult formula). This might seem more powerful at first, but beyond the 50 mark the damage increase decreases very quickly, so that by 100 quanta it deals only 20 damage, compared to the current Firebolt which would deal 33 at 100 quanta.
This is what I propose instead of a quanta cap. This allows Stone Skin and Fractal to continue to be used to the fullest, but still nerf Firebolt so that it doesn't rack up damage so quickly. Compared to Catapult, which requires at least a two-card setup (three for Catatitans), and is vulnerable to both PC and CC, the direct damage Firebolt which only requires the card itself and enough quanta should have a much "weaker" formula. It also doesn't "reward" the player for blindly hitting spacebar until they reach a certain limit, and instead encourage them to think -- something that Firestall decks don't require much of.