And, as shown with the first graph, if there was significantly more cross-region play, it would fix the matchmaking since it would push everyone towards their true MMR relative to the world rather than just their region. Players in low priority will not gain battle points from the match, will find games more slowly, and will only be put with other players in low priority. The skill distribution and MMR would be consistent, and would look like something like a bell curve note that the numbers aren't the same scale that dota 2 uses: Beating someone way over your skill level changes your ranking much more, than the very tiny boost you'll get for beating someone only slightly over your skill level. What pool you are in is determined by the region you selected for example, US East, Europe West, etc
I came up with a Dota 2 video in which the video maker compiled his trolling gameplay.
DotA2 Matchmaking System - How does it work?
With the exception of bot games, matchmaking is mostly determined by matchmaking ratings MMR. Valve has not disclosed how these scores are calculated, but abandonsreports and commends seem to play a role. Most players report having an account flag value of 0, 1 or 3.