The value of a proc is not simply the mana gained from the Verstone/Verfire. Since the spells are GCD, casting one means pushing out another spell that could have been cast in that GCD, almost certainly a Jolt. Since you're sacrificing a spell that gives 6 mana for one that gives 9, the value of the proc is actually only +3.

I agree that we wouldn't want the best finisher to be so good that it makes it worth overcapping or ignoring procs. There should be situations where Verholy/Verflare are correct, thus creating gameplay by allowing the player a situation to evaluate and a decision to make. I put in some rough numbers, but those could easily be tweaked to produce the desired effect.

Changing the phrasing on Verholy/Verflare doesn't quite achieve the same effect. The proposed Scorch gives the player an extra, harder situation to aim for (with a higher reward for hitting it). Changing the existing finishers would simply remove the need to set up unequal mana, so you'd actually have fewer things to take into consideration during gameplay. "I don't need to worry if my mana is equal or not" isn't the same as "I want to set up my mana to be equal".