Rating system for online games in Heroes of Might and Magic IV.

As they say, strength lies in numbers. On the contrary, this will show the player's activity. Where is the unfairness here?

No, that's not it. For example, one player participated in one tournament and scored 3 wins and 1 loss. Another player participated in several tournaments and scored 12 wins and 12 losses. According to the rating, the first player will be ranked higher, even though he may have faced weaker players than in other tournaments. Will there be a rating decay to balance such players? Will "non-participation" be taken into account, because not all players can participate in every tournament?