I think they should revert it without any other changes. Developers know what are they doing. They "calculated" how gunblade works in FFXIV, and made perfectly fitting sounds. Gunblade is not a big sword, and it allows for very swift attacks. In original sounds you could hear slicing, pulling the trigger, mechanical sounds of the gunblade, and of course explosions.
It can't sound like hammer or club. Even DRK sword doesn't feel that heavy. And explosions can't be too loud because it would be irritating very soon.

I think GNB is a victim of nostalgia. We are not in FFVIII. We are not Squall or any other dude from this game. And keep in mind this game has pretty much over 20 years now, so sound quality was certainly low.
Developers shouldn't make such drastic changes so fast only because vocal minority had issues. I bet they would stop whining pretty soon and enjoy the perfection of GNB. Perfection which is currently lost.

Reminder to send them suggestions via in game support menu.