Anyway, for all the firepower and durability wank, speed and reaction is their greatest assets. This is why slow, ponderous unit like Panzerkannone is worthless. And Golems are so fast that their massive firepower and/or durability is pouring salt to injury.
So I guess CONSTANT salvo of GAU-8 will chew through I.S., but their speed is that hax that not many bullet will made contact.
And by nature, AA missile work by proximity detonation either sending shrapnel, metal pellet/cubes, or an expanding filament web, it's weaker than individual vulcan bullet in destructive power. They work on most aircraft because most aircraft armor are are cardboard thin.