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

Or maybe just count the number of wins a player has in all tournament games. A draw is worth half a point. Losses don't count. Therefore, a talented newcomer who has won a couple of games can be ranked the same as an outsider who has played many games but unsuccessfully, but they definitely won't be near a veteran who has, for example, more than ten wins. It's simple and doesn't take much time.
Or is it too simple? Although, with your formulas, you could go crazy (I don't think you'd like to do SO MUCH calculating)!