Hard to say, it's listed in the modifiers list I made which means I must have come across it at some point.
If not I can always just do as you say and either add a huge cool down or a massive damage reduction to the two mentioned skills.
A damage reduction to GoH most likely wouldn't work, since that would only reduce the % modifier of the skill, and not touch the missing hp damage at all.
A knuckle arrow hat does sound fun though. Flash combo really does do what the focus beret was supposed to do anyway, so I agree that combo doesn't need the buff.