I had a guildie who faced an R7 GAS. His was 6*. Any matchmaking that pits someone with a 37k+ GP character versus someone else who doesn't even have a single character over 30k needs some work. Counters work - but it's still a tremendous advantage.
I always find it amusing when people decide to argue that matchmaking works great - despite all of the clear and obvious evidence that devs are fairly inept about many of aspects of the game as shown by all the constant bugs, nerfs, "unintended interactions". Sorry, I find it very difficult to believe and accept that they miraculously got matchmaking right, in a constantly changing environment that didn't even include relics at the time. It needs a great deal of work. Claiming it doesn't is as misguided and naive as those who think drop rates are manipulated.