Melee is nothing more than the last resort to push away an enemy or two when you get swarmed and can't get a clear shot. Stealth, it depends on whether or not you need to save ammo and resources. On survival it's not always needed, but in Akumu it will be your best friend. Of course, accessing a game's mechanics based on the highest level of difficulty possible is not the best way to do it, but yeah, stealth is needed in higher difficulties cause you really don't have ammo to spare and they kill you very fast in open combat. It's not worth the risk