my opponents were both rated around 580. In reality, one was a much better player than the other; presumably they always played 2v2 together thus always won/lost (rating) together
Yeah no rating system in the world can really fix that (if they indeed always play together), unless it measures other things than win/loss, which would open the door to people trying to game the rating system (potentially grieving their teammates to gain points) instead of trying to win.