It seems that matchmaking is not the problem here. Roster development is. If you are 500k GP ahead of your opponents, but don't have the META characters, they do, you can't really blame it on matchmaking.
Ironically, there may be players complaining here on these forums, that they get matched with you, since you have higher GP. All while having a fluffy roster is not the disadvantage i used to be in GA, and it's also not an advantage in GAC unless you have the META characters.