you REALLY need jolly on terrakion. you outspeed Modest Venusaurs in sun, scarf Jirachi, genesect and actually have a chance against scarf keldeo/terrakion. it's not only for scarfmence.
Additionally I'd like to suggest removing 4 hp EVs on rotom and adding them to Def so Genesect gets a Spatk boost. CB Genesect can cause some problems and giving it a useless boost will help combat it.
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wish i could change my username to chimpact :[