To be technical, Sound Designers are given pretty much just archetypes to go with and told to do it. They don't have to worry, like with weapon design and the stats, it being too powerful or too weak, only if it evokes the right 'emotions' or a feeling of awe or happiness or whatever. They just do music and only fix it up if need be. They'd likely be done first, then Terrain Makers and whatnot.