Hardcore ? You're not doing things right maybe. The nerf is only when you need to snipe without having time to pick up ammo, so the warpriest or Golgo. And that's all I think. For all the other boss, you have time to use ammo from your inventory or just to pick up ammo on the ground. Also for Golgo and the Warpriest, you don't need the full time to kill the bosses. Otherwise the strategy is not good OR the guys are just not ready. Their light is still too low for example. Or I missed something. Btw I'm on PS4 so I can't help you to teach how to kill those boss without problems. But I know a few good friends who have PS4 and XB1 who are usually helping beginners.