Trials matches you based on wins on your card. I have been matched with similar teams (2.0+KD) on my first round and other times with teams that have never competed in trials. The competition is supposed to get more difficult the more wins you have. I have noticed skill level jumps at 5 and 8 wins. Also, the trials community, at least to me, seems to shrink as times goes on and then when an expansion or DLC hit more people play and the pool gets larger. I would recommend playing trials a lot when ROI hits. I always seem to have an easier time getting wins during those times.