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The initial idea is that games in short game modes (especially arenas) should award less rating, as it's unfair if a 20-minute game and a 6-hour game give the same amount of rating (those who play 20-minute games will gain rating much faster).
In my opinion, ideally, the coefficient should depend on the map/template: on all maps/templates except for a few built into HotA, it would be minimal (or even zero), and on these built-in maps and templates, it would be set manually by the team depending on the usual game duration, the balance of the template, and the team's desire to popularize a particular template (judging by the G+U incident, the latter seems to have worked).
However, only baratorch can make changes to the lobby, and he doesn't have much time, and also has his own views on things. Therefore, I wouldn't count on any complex changes, but simple adjustments seem realistic.