I think matchmaking is broken not only in rivals but even more in gauntlet and other tournaments. I played all 14 gauntlet entries and lost nearly all matches against much higher skilled opponents. And I failed to win the tournament even once. There is no elo or form like WL. Matchmaking is random and does not put into account your prior results in those tournaments. Season 3 evo cup is a nightmare for me. I can easily tell from the way my opponents play that they are way more skilled than me yet when I lose against them I get matched up with similar level opponents again almost every time. Until now I couldn't complete the related objectives and I've given up trying. Now all I do is score a goal against myself one or two times in order to send a message to my opponents that all I want is for you to give me a donation and let me score a goal so that I can do the objective requirements. And it works.
It shouldn't be this way but because EA fail to balance matchmaking you are forced to think of alternatives.