To see them, I separated the 4882 1-5 ranked EU players into 5 equal sized groups by increasing winrate. Then I did the same for increasing XP, creating 5×5 groups. Counted how many players are in the various group combinations and what is their average rank
In the player chart I colored fields blue if they had more than their fair share of players and red if less. As expected, most players are on the diagonal: they are just as good in XP as in winrate. The highest XP & lowest winrate group (the home of the mythical star savers) has the smallest population, exactly 16 players. The opposite (highest winrate, lowest XP) has 87, so it’s more likely that they are just random outliers instead of a purposeful meta group. The “second highest XP, lowest winrate” group has 124 players, but the “second highest winrate, lowest XP” has 159, so it’s also just random noise.
The second chart explains where they myth came from. Rank is more determined by XP than winrate. Being in a high XP group is more important than being in a high winrate group.
How can both statements be true? Because the XP formula is well balanced and anything that gets you XP also gets you wins. So those who do good damage are actually good players who carry their team. 55% winrate is great, but it means 45% loss rate. In these 45% games their teammates might flame them and call them “star savers”, while their only fault is being unable to carry the flamers. Them saving their star is well deserved, they were the best player on the team. The mechanic is a well designed one that saves good players from the consequences of MM giving them bad teammates.
The “high XP low winrate” player do not exist (in statistically significant numbers). So the myth isn’t simply untrue, it’s actually harmful. It places blame on those who did the most to win. It’s not a surprise. In every game the baddies blame “the team” or the good players for their own fails.