If you decide to take out Mew (just in case you do), add in a few Silent Lab, to slow down decks which use basic abilities, even decks which have 1 or 2 Shaymins.
Like that you are using Octillery to get consistency instead of a temporary boost Shaymin, doing the same in my deck. Anyways, on to the deck, in my opinion it would be good to add in a Hoopa EX to get your bench loaded very quickly with Glaceon and Jolteon.
Yeah, I just added that in as I already had that card. I know you were originally suggesting Shaymin for this deck, but I hope you see that with my new deck Octillery fits in better. :D
What is better with Baby Volcanion is that he can take care of himself, - has strong attacks, good hp for non-EX while Camerupt has a 3 energy 60DMG attack, so if I end up with Camerupt it will become harder to damage the opponent.
Well that works if you want something other than a pure Talonflame, the only thing is running all those Cyndaquil will reduce the chances of you getting a starting hand of Talonflame.
I have almost purchased all of the Pokémon I need for this deck, for example - x2 Volcanion EX, x3 Flareon EX, x1 Hoopa EX, what's left is buying x2 Remoraid and x1 Octillery, possibly 2 Octillery.
It will allow me to loop energy, here is how.
Steam Up - Discard Energy + 30 Damage
Burning Draft - Get Energy on to Camerupt
Flash Fire - Get energy onto Flareon EX
Which means massive damage to the opponent's pokemon. :D