Player rating for tournaments across all installments of Heroes.

In total, the winner will receive exactly 50+50=100 rating points.

Well, if we leave it as it was: (100+100)/2, the final number won't change..., but a 100-point system is somehow more familiar...
But this isn't a critical issue, and it doesn't really matter how it ends up... ;)

That's true. But there are 2 ways:
1. Use an existing system (like VDV Forever or some other sport, for example, motorcycle racing, multiply by 2 and end with 1, 50-40-32-26-22-20-18-16-14-12-10-8-6-4-2-1-1-1..., by the way, Alan and others have already mentioned it).

Oh, these "ceiling" numbers... I, by the way, don't like such a large gap between 1st and 2nd place...

2. Write a formula based on the place, or maybe even the number of participants, like in an oscillator, but so that it's more gradual.

Well... about the logic, you're exaggerating... :D
Because the existing linear formula is much easier to understand than:

writing some power from 0 to 1 and getting any curvature of the curve.

Believe me, only a few of those present on the portal will understand this... :D

With the introduction of this formula, we need to think... but not about the formula, but about the philosophy of our system, i.e., we need to clearly define and understand what we want from the rating! Who should it encourage, and who should it punish. And after that, it will not be difficult to write a formula that satisfies our criteria... ;)

Sincerely.