When I battled him in X, he got pretty unlucky. My Haxorus OHKOed his Clawitzer with a critical hit Dragon Claw, then my Houndoom lived his Starmie's Surf with 4 HP after he used Light Screen, and Gyarados used Dragon Dance but my Lapras paralyzed him with Thunderbolt. But in Y he was only annoying because his Clawitzer kept confusing my Roserade with Water Pulse. My Tyrantrum's Quick Claw activated against Gyarados and OHKOed it with Head Smash, even after Intimidate. Drasna didn't have any really powerful attacks other than Noivern OHKOing my Haxorus with Dragon Pulse. Malva only had me worried because of that Chandelure. Wikstrom I kinda went easy on just to see what attacks he had, but he was still pretty simple also.
But yeah, they really should have had five Pokémon this time around, with over 400 Pokémon in the Pokédex there really isn't a solid excuse.