Garde sets up, Empoleon attacks? Garde LV.X brings down everything that's not dead yet?
Iono, I kinda like the fact that nothing can OHKO a Garde/Gallade without Battle Frontier. Hence why I like healing first, then Bringing Down (if you're at full health, obviously the opponent will be closer to dieing) for the win. The deck most certainly would want a maxed out Garde line (to abuse supporters, Gallade's massive active slaughtering ability) and then use Empoleon as 3-2-3 or 2-1-2 support. Most certainly.
A slight flaw you'll experience is that Empoleon won't be able to Cessation Crystal, allowing power decks to come back with a vengence against you. Gardevoir's Psychic Lock will help slightly, but you'll definitely need to tweak your trainer/starter line either for quick pokemon set up or stalling.