@Kearvahn HiRez gave up on e-sport for Paladins. I am not sure what's up with the matchmaker. Maybe it takes into account, how many reports you got or how much money you've spend. It became very weird lately.
You can see that single players win 48% of their matches while groups win 50-51%. So grouping up can improve your winrates, also because the Match-Maker can't target you anymore, if you are in a group.