Here's how I beat the Multi Battles.
Adamant Multiscale Dragonite @ Lum Berry
252 Atk / 4 SpD / 252 Spe
Outrage/Earthquake/Extremespeed/Dragon Dance
Brave Aegislash @ Leftovers
252 HP / 176 Atk / 80 SpA
Shadow Ball/Shadow Sneak/Sacred Sword/ King Shield
Jolly Mega Kangaskhan
4 HP / 252 Atk / 252 Spe
Return/Fake Out/Sucker Punch/Power-Up
Always use Tierno as partner. Start with Dragonite as lead, Kang second, then change the lead to Aegislash once the random Ice shit starts rolling in.
Also, here's the list of enemy Pokes, in case no one else has linked yet.
https://docs.google.com/spreadsheet/ccc?key=0AgSyZW1zYKNJdFA0cTlFMGxhVm1YSlFkaGRoMzlmZEE#gid=0