Just to point out the answer on a former question: the ladder has been changed from weighted rounding mode to straight rounding mode. The amount of luck % was 0 on both versions. The difference: on 0% SR 3vs2 always work, on 0% WR 4vs2 always work, 3vs2 work with a chance of 80%. Not the amount of luck %is that important, but the rounding mode changes a game drastically.