Gaming

I don't think the 1000 rounds per minute would make sense in any scenario other than a movie or video game. If you're going to the trouble of carrying all those extra barrels around, you want to be firing at a rate high enough that a single barrel would overheat. But, if you're firing at 2000+ rounds per minute, the recoil quickly becomes unmanageable for someone on foot.

Multiple barrels makes sense for a CIWS gun because you're shooting at something flying at you extremely fast so the time it's within the gun's maximum to minimum range is short. Similarly, it makes sense on a plane, like the A-10, because the plane is moving fairly quickly and it might not be able to aim at the target for very long. In both those scenarios you want as many bullets on the target in the short time window you have.

For a door gunner on a helicopter, I imagine the main goal is to suppress the enemy. Accuracy is less important than keeping their heads down. You want one man to be able to suppress possibly a platoon on the ground. The weight of the gun doesn't matter since the helicopter is carrying the weight, and the amount of ammo it uses isn't too important because the engagement will be pretty short (just enough time to get in and get out). So, a minigun makes sense because it can send a continuous stream of bullets into a general area for tens of seconds without running out of ammo or overheating.

I can't imagine a scenario where it makes sense for a soldier to be able to carry and fire a minigun while standing up. Maybe there's a scenario where it's a crew-served weapon that you carry and set up quickly. But, even then, surely 10 rounds per second is going to be enough, and all the extra barrels are just weight you don't need? The only time I can see them really being useful on the ground is defending an outpost of some kind. There have been scenarios like that where the engagement lasts so long that machine guns overheat. 1/6 of the heating and 1/6 of the wear and tear on each barrel might make the extra complexity, weight, and electrical requirements worth it.

Someone posted an excellent video of what the recoil is actually like. It fires the same rounds as an M14 rifle. So, per round, it has the same recoil force. Because the gun is a lot heavier the acceleration of the gun due to the recoil is smaller. But, the force per bullet (or the impulse) is the same. The greater number of bullets means that the total force is higher. But, it's smoother because of all the extra mass.

The end result is that an M14 slams into the shooter's shoulder, but the minigun is like a gridiron football player trying to shove the shooter backwards.