Over the next few weeks we'll be experimenting with toggling strict solo queue on and off, to see the impact it can have on match quality and matchmaking times. The primary reason we initially added this feature was because there was a much larger discrepancy in motivation between players competing for solo MMR and players competing for party MMR, resulting in a poor experience overall. This discrepancy is not as pronounced now as before, and each option that does a hard split of the matchmaking pools has to be considered carefully as it has a direct influence on the matchmaker's ability to find the best matches available.