Collecting the previous posts and arguments while absolutely thinking that the basic idea in general would absolutely be beneficial.
The counter-arguments to a map-based rating are absolutely correct, but maybe it's possible to find a solution that helps without destroying anything.
Practical approaches:
- It only matters for the map i currently want to play - if someone plays this the first (or say < 5x) time could be marked somehow - as it could be marked if a player played it 100x or 200 or even 500 (imagine a color indicator) (i absolutely know that this is not the "best" approach but i would definitely pay attention to such a badge)
- if one could "activate map-based rating"(like a game mode)
2.1) maybe it is somehow possible that locks a lobby from map-change later (there is already a pre-pick! Or IF changed later, that mode is auto-turned off...) ?
2.2) for that particular game mode the set of maps are just hand-picked (look how often the same maps are played) so that would totally beat the duplicate/half-duplicate/whatsoever map-problem.
Of course, it's not a solution already, but imho going on with thinking about it is really worth it and if we want a better rating system we cannot ignore the important map-to-rating relation and we would stop "rewarding" people to train a "i only play mid on XY-map"-behaviour (yes, spot-based rating would be even cooler!!). I would very appreciate if this overall discussion about rating would be continued with a good structure. This topic is (and should be) a long-term task imho.