I pretty much wrecked the elite four with a planned out strategy.
Steel: Blaziken pretty much had this from the start, taking out everyone with his fire and fighting moves.
Water: Rozerade could take this team with an arm tied behind his back. The only trouble was Gyarados, but my Rozerade's speed was better, and took it out with a quick Hidden Power (Rock).
Dragon: My Mega-Blastoise tanked the entire team with ice beam, and if when he fell, I had my Lucario to finish up the scraps with his Speed and Attack power.
Fire: Blastoise also had this one for the majority of the fight, falling only to the Chandelure at the end.
The champion wasn't too bad, and I was pretty prepped up for the fight, but that Gardeviour's speed was nothing compared to half my team.