Player rating for tournaments across all installments of Heroes.

to IronAxe: I've been meaning to say this for a while, but I keep forgetting – there's another drawback to your system... it can't be used to calculate a rating for a tournament like "Arena." Because in this type of tournament, the player's placement is what matters most.
This relates to your plans for:

Especially if you think about an overall rating among online resources.

Best regards.