We (combined GP ~100 million) got burned by a guild with WAY more powerful players. we are talking several G12 7/ NS and ewoks squads, a guildleader with every toon at 7* (except hermit Yoda at 5* and Wampa) just to give a few examples of the level of p2w.
there was no way we could have won, we could have made a tie if we had inserted bad defence teams. But who plays to get a tie?
My guess is that they only participated with some members to keep their collected GP down. a clever strategy to "come down" to a level were it is possible to actually win. I have no idea of how they convinced the rest of the guild not to participate
They gamed the system and I don't blame them. But it shows that the matching formula needs some tweaking.