@Jargs while I agree that there are a lot of unbalanced skills, none of them render other classes almost unplayable. To be honest, those classes mainly affects the entire builds that ends with Sage, but that could end with anything else.
I understand that this isn’t a strong point, just that a lot of things are related, Missile Hole itself is a great support addition to any of those, to the point it gets unbalanced.
I honestly think that adjustments that keeps the skill strong (instead of overpowered) as defensive skill will make it good and still nice to play with those builds.
How much do you consider to be high uptime? To be honest, I think that 50-60% uptime is fine for Missile Hole, as long the buff duration is low in a way equivalent to its uptime, so it requires timing, grouping and coordination to be used after initial buffing stage. (Example: 30s duration, 50s cooldown, even on Missile Hole on its current state wouldn’t be too harmful to archers anymore while still good if used correctly.)
I agree to some point that Gohei is too overpowered, maybe it should have higher cooldown, less overheat, smaller range and/or don’t affect ground skills while being still strong to remove self buffs (such as MH in question).