yanmega is awesomely annoying, not that hard if got delinquent in hand.
also for me i still use energy on my yanmega jst in case some pokemon with ability lock or some attack with ceratin abilites lock.
if i got that many shaymin i can jst use team flare gear or team flare net(not sure the last one name, its tool that decrease pokemon attack by 20) to make that yanmega more painful.
preferably ariados and sceptile with hidden shot?(forget skills name) is to combined with this yanmega, since both use very little energy. but its kind of wasting precious space in deck, i think something to stall energy like hammer is better it could help with lucky flip. but it will wasting more space if got really bad luck.