[2019] Korean Challenger matchmaking issue has been fixed.

Meddler is going to talk more about this in his weekly post, but we made some tuning changes to our matchmaking for Challenger/GM/Master. When we're looking at really highly skilled players, there's not a ton of options available to make a match, so we're usually balancing long wait times with closer matchmaking. The previous tuning was definitely skewed more towards fast match times than it needed to be, so we re-tuned.

This was done globally and not just in Korea, but the specific tuning has to be done uniquely for each region to reflect that region's player base. We'll continue monitoring match quality and queue times going forward and make adjustments as needed.

This specific tuning value isn't like an on/off switch - we had a previous iteration of the change a little while back and we wanted to let that settle before making another change. We got the results we wanted in some regions but not in others, so we went for a bigger push this time around.

For the specific D4 problem you mention, we do have demotion protection systems in place that make it harder to demote across a Tier. Also, looking only at winrate loses a lot of the context of how a player is performing - specifically, who those games were against, how recent the performance is, etc.

When we say "streamlining division sizes," that doesn't just mean the actual headcount inside that division. It's a consideration, but we also want to look at the skill disparity inside that division, and that has actually improved this season. Having high skill disparity in a division makes it much harder to climb through that division, and that was a big part of what we wanted to address.