I don't even play MCH all that much and already could tell the changes they've made are failing to address some fundamental issues.

MCH wants heat, because more heat = more Cooldown usage = more DPS. Buffing Hot Shot's damage bonus while simultaneously reducing heat generation and the amount of Cooldown usage as a side effect is making the actual DPS increase they got smaller then it should be.

As it stands, overheating is still a penalty instead of a benefit in almost every situation, and still horribly punishing compared to the mistakes other classes can make. This could be fixed by simply bring the overheat damage bonus back up to 20% like how it was in pre-release Stormblood builds.