I fail to see how Magearna is good against Yveltal-EX, but if that's what works, then sure.
It does make me question the point of this thread, though. You seemed to have had your answer from the beginning, at least from what I can see. Though, maybe this helped you figure out that Magearna was the way to go, in which case, good.
Either way, I'm out of ideas at this point.
-Asmer
Magearna-EX doesn't do well against Yveltal-EX or does anything unique against it. I just have to hope I don't start with it but the matchup isn't all that bad since Mirror Move is a good attack to use assuming things go well. My goal of this thread was to see if there were any options out there that aren't so luck based at controlling energy in play without playing a completely different deck but it does seem right now that flipping coins is my only real option at controlling them, which sucks but I do thank you for the discourse because it helped me in deciding what I should do with the deck.