It will also mean you will lose less CSR on your losses because if your MMR is higher, the CSR update assumes you were more responsible for the win, and less for the loss. Likewise, MMR can go down if you perform poorly compared to the rest of the players on your team, or in your party, resulting in eventual CSR losses.If I remember correctly, in the previous system, to offset the potential rank shifts that would occur with allowing the matchmaker to expand skill ranges when matches (to compensate for lower populations), losing a match where the skill system predicted you would win would result in greater CSR losses, while winning a match where you were predicted to lose would result in greater CSR gains. Has this been done away with with the implementation of Trueskill2? Or, is Trueskill2 competent enough to tell when an individual player performed better than expected compared to the team expectation? The way you describe the potential of losing less CSR on a loss when having high MMR seems to contradict that previous idea of increasing CSR loss when losing against someone of lower skill than you. Hence my confusion.
In MMR land the loss / gain takes performance into account.
In CSR land, you can still lose a lot more if you lose a match you were supposed to win.
But, what I mean here is, when we do the update we look at your teammates. Whoever has the higher MMR among your team tends to get more points for a win and lose less for a loss because the CSR system assumes the higher MMR players are doing what they should be, etc. It's pretty indirect though. So if the matchmaker has to put a potato on your team, the CSR update will understand this and not dock the player as hard.
But, if a group of like-skilled players loses to a group of bad ones, yes, everyone's CSR will still drop considerably.
This will still happen to the very top players quite often as they will find themselves going +1/-29 with 29-1 records and staying at a similar CSR. It's not that they're losing points unfairly though. They're just staying at the same level.