Hmm, tough claws will power up the triple fangs by 50% and adamant, attack and speed evs helps sweeping. I advice you to use this . Def doesn't matter. And the trainer on USUM don't use mega evolution too much if you aren't playing online. Volcarona is good, but you may give him some HP EVs by lowering SP. Attack.
Also, you can use a pelliper, politoed, kyogre or any rain caller Pokemon for making hurricane non avoidable. If you use it on rain , give him scald instead of fiery dance, it has a 30% burning chance, but note that fire fang will deal low damage.
If you're using volcarona on rain ,switch aerodactyl for mega scissor. Mega scizor's only weakness is fire by 4×, but rain will make it 2×.
And scizor has 150 attack that become more powerful if you sword dance and mega evolve. It has bullet punch and a lot of resistance. If you use aero in rain, it's weakness to water will become 4×.
Now you have two option: Rain volcarona with Scizor or normal volcarona with aerodactyl.
Any tips and corrections are welcome.