I know this is old, but there is a point of having the quick play be a factor as well, just not nearly as significant one as op indicates. The comp system has a lot of people complaining about it, and people that are dissatisfied will likely be going with quick play at least for loot boxes and possibly to keep their skill upish until the next season. In this case, quick play should be a relevant factor in deciding the placement ranking.

The huge difference the mmr made in deciding the sr despite a clear disjointment is quite an oversight, however. The system should have seen the discrepancy between the projected sr and the mmr, and reduced the weight of the mmr accordingly. Really, there should be two different mmr rankings, one for a high average performance and one for a low average and a stat that represents how closely related they are (between switching between these averages within the last 50 or so games, them being about the same between formats, whether you usually have that one character for most of the game in one average but not the other, etc.)