Sorry about the whole Rock Slide thing, I didn't know the TM was obtained after reaching Kanto. Anyways, why I was saying that Mamoswine could manage beating most of Lance's team was because of Dragonite's x4 Ice weakness paried with Mamoswine and Dragonite's equal base Speed and Mamoswines incredibly high attack, Mamoswine should be able to outspeed and OHKO them. Mamoswine will also gain levels from the rest of the E4, insuring that each Dragonite will be finished off. Ampharos should be able to 2HKO Gyarados with Thunderbolt, and the rest of the team should be able to handle Charizard and Aerodactyl.