Don't think about JRPG logic too hard. We knock people out with giant claymores and they aren't mortally wounded. You also have inconsistent uses of powers. For example, Nael Darnus in a cutscene flash steps behind an Eorzean Alliance officer and kills him before he knew what had even happened. Why didn't Nael just kill the player in an instant during his boss fight? Or how Fordola can also flash step in a cutscene, and then never used that power again to kill the heroes.

As for people tanking machine gun rounds, we saw in one HW 3.0 cutscene Hilda try to shoot a Heaven's War night, but he had protect up as a shield and the bullet did nothing to him. I suppose it's like the shields from Dune where the faster an object is traveling, the more resistance it meets from the shield. Thus, super fast bullets are deflected, but relatively slower sword strikes can pass through the shield unobstructed (thus justifying cool melee combat). But we never see that protect spell ever used or mentioned again to counter bullets, and in Shadowbringers 5.0 a certain arch magus is shot in the back, so again inconsistent use of powers...

Really, don't think about it. JRPG combat makes no sense.