I think the fragments hidden in the campaign are a bit much as some of these you’d never find without looking it up or getting lucky (specifically the one in Iconoclasm) and most players don’t go and replay these missions constantly. The ones in the world are mostly fair. You should quickly encounter both light and dark vestiges by following the quests given to you in the post campaign and then they literally tell you where to look. The prismatic chests in the world aren’t particularly well hidden, and once you find them it’s fairly obvious you must do something in the world to unlock them. I think the one all the way in the Lost City Outskirts is a teensy bit unfair (because you’d almost never go back there and very few people know that their ghost has a reaction when near a collectible) but there are pathfinder objectives in the area and stuff so it’s not completely unimaginable you might go back in that area. Edit: I think especially too with the campaign ones, the campaign is already fairly long even at an average pace so if you decided to spend time exploring for the first four missions and found nothing, you’d probably have stopped.