X-Scissor should be replaced with Bug Bite for that Technician boost (M-Scizor)Oh, and do you really need 3 Dark-types and 2 Fairy types? Xerneas should have Thunderbolt instead of Outrage as you're running a special set, and Outrage doesn't really cover any of your team/Xerneas's weaknesses. Lastly, no bulky mons? For Azumarill, Return isn't really needed. Superpower instead for Steel types? If you feel Greninja is a little too slow, you can use Water Shuriken in place of Surf as it has +1 priority. I don't really recommend it though, as it is rather unreliable, ranging from 30-75 base power, which is still 15 base power.lesser than Surf. Anyway, Greninja is already rather fast. I think you should also replace Yveltal or Darkrai with a bulky Pokémon or something to cover your weaknesses.
