While matchmaking does pull from the top 80 toons, it clearly has blatant issues. With his 29 R7 toons and a total of 52 ish relics against my 6 R7 toons and a total of 35 relics, it clearly favors the opponent.
Not only can they field more teams, but those teams have a much much higher probability of full clearing my entire defense while having a lot leftover for defense. Especially in 3v3. GAC was created before relics and Galactic Legends, and I firmly believe it needs to be changed to matchmake only those with Galactic Legends together and have a similar number of relics. Why should they not?