That should be the hint that these are inexperienced players who have ubers simply because they are legendaries, or they heard they were unbeatable. They're probably not IVd or EVd either, so it's not that impressive that you're winning. Also, Aura Sphere is not the strongest special attack in the game; it has 80 base power. Yet another clue that these aren't legit ubers teams.
I guessed that was the case. And I meant Mega Mewtwo Y has the strongest S. Attack in the game, not Aura Sphere.