Player rating for tournaments across all installments of Heroes.

With the "bicycle" you mentioned, which you are trying to "redesign," it's much simpler. There is a universal unit of measurement, such as hours, minutes, and seconds. In Heroes, however, there are days, experience, and skeletons. It's simpler there – all this data is summed up. In our case, you are essentially suggesting summing days, experience, and skeletons (exaggerating).

And it is unlikely that anything similar (a universal unit) can be found for this system in Heroes (the first thing that comes to mind is the points for the map, which the game itself awards).