I've played 12 online matches against other players now and despite winning all of them, I have hardly progressed towards bronze rank. Most wins my rank will go down by 1-10 points, though one time it dropped by 168. It does appear to be related to how many players remain at the end of the three rounds, but there is still quite a range of variation left. Perhaps the difficulty of the maps is taken into account. Does anyone have any other insights into how this rank progression is determined?