Amphy-mega is like, one of the best team mates for crocune there are. Since cune has trouble against Heliolisk, the now-gone Zapdos, and can be used as setup-fodder for dd Gyarados, Ampharos can most of the time get a free switch for mega evolving on them. In exchange, Suicune can help vs swampert and Aerodactyl-Mega, and CroCune can also deal with special walls such as Blissey and non-cm Florges. Point is, together they perform a good balanced core. As teammates I would recomend strong fire types that can deal with Whimsicott and Hydreigon, such as Entei and Whimsicott itself.