@AceTrainerAlex, well I can't really say I have any issues with the deck, it runs nicely. I feel like what is nice with the build is consistent performance. Occasionally you will miss an energy drop, not get out your Megas quickly, or have to stall behind Xerneas, but these aren't terrible flaws. You also, will never have to worry about having a lack of energy in play like you can with Darkrai.
Max Elixirs are kinda all luck, you can't really do too much to fix that. 10 Fairy Energy would help, but not too much. The big thing is to try to deck thin, by using Ultra Ball and Sycamore to get out bad cards from your hand, and then using N to draw up some more cards. Even this only helps out marginally. This is a big reason why I dropped this card from 4 to 3, it being used as a main energy accelerator is inconsistent. You don't need to hit all four types of Energy acceleration in one turn, that being Geomancy, Attach from Hand, Max Elixir, and Mega Turbo, you just need to make sure you are consistently putting down energy.
The new Basic EX seems pretty good, the second attack being able to one hit Shaymin, practically anything with Fairy Weakness, and most importantly, a Giratina with a Fighting Fury belt. The first attack is also good, however a bit conditional, I might miss the healing of the current one, but it never really mattered outside of the Seismitoad match. I will probably switch all to the new one, once the set gets released. I might switch some back, if Metal decks pick up steam, but until then, the new one is overall better. I don't think the new Mega is that good, while it does have the advantage of being able to hit for Weakness for Psychic and Fairy, it doesn't put out that much damage. The ability of being able to avoid your Shaymins and Hoopa being sniped is nice, but I like the consistency of 3 way to much. Might run if a Psychic weak deck comes up, besides that, probably not.