The top palkia lists (jayson h, etc.) run toxicroak g promo to 1hko a luxray after Luxray has KO'd a Palkia. Not an autoloss by any means, especially when Luxape's other attacker, Infernape, is x2 weak. Stuff like Luxray/Manectric or straight Luxray would beat Palkia pretty consistently despite toxicroak g promo, however.