The most important change to make PSR work better, I think, is the nature of how gains and losses are applied.
Quite simply, your PSR should not change if you perform near the team average on a win or a loss, with changes being based on how far you exceeded or were outplayed by your peers. Circumstances in games can vary wildly and so can the player mix. In many circumstances your team's overall performance will inflate or handicap your match score. In short, eliminating the notion that you can increase PSR through being carried while also not decreasing PSR of those who are on the receiving end of a stomp, where the entire team fares poorly.
PSR should put you in the correct place and keep you there, rather than this notion of slow progression. I like the present philosophy of weighting some towards wins to account for some poorly rewarded behavior that does help the team win and selfish behaviors that contribute to losses. So, for example, something like this:
- PSR increases above 10% of the average match score on a win, and on a loss 20%
- PSR decreases below 20% on a win and 10% on a loss.
There are multiple (and more complicated) ways to enact that concept, but this would in theory balance out if your win/loss was 50/50, as opposed to being a net gain over time. It would trend up or down with two factors: your individual match scores, and your win/loss rate.
Next I think we would need to make PSR adjust more quickly.
Since PSR is currently based on a comparatively huge sample pool, it responds poorly to changes. In particular people who are in the wrong place take ages to move one way or another. I think I'd be in favor of tier being related to a rolling average of your last 20-30 games instead of a cumulative point-gain over time, or at least the number of games required to move tiers being reduced to a similar number. Even decaying over a long bout of inactivity.
The system should respond faster to your performance than it presently does and your tier should relate to your day-to-day play. This sort of thing also has the benefit of scaling with a player base that gradually becomes more experienced.