Good point, always forget a power or two. Storm Skald could make this more potent with Thunderous Cleave.
Heavy weapon tag on a support charmer is a sad sight in my opinion.
Sadly no as far as I know. Azzy's Poison Edge power could be abused along with Rin and the swords maybe?
Burn order with Deflagrating Touch is weird as the infinite burn makes all other sources lesser once in place but if applied after a timed one it sticks around still.
Are you set on hex Cait and Spirit Arona? If you want to try others I did a write up on all of them
here. Support charmer fits well into a tank and healer set up with some wiggle room in Vestal Cait, Double damage can be done with support of Crackle and Kunai to help proc Twist the Knife and get a free turn. Support can also get use exclusively with Thief due to Eye For Weakness, it depends if you really want those longer debuffs. With support charmer the debuffs are fine but the buffs you can apply to the party is the main idea with some support debuffs that can be mixed in.
My main support set was for a bit making use of FoxFire, Acid Flask, A buff power/Allure and Roaring Storm. Acid Flask or Estrus Flask for cunning use along with Roaring Storm and FoxFire for chip, the last slot could be a buff power or the flask could be switched out for it and then I would always try to run allure for damage. The set can be readily changed to do more with buffs but the backbone of Allure was important in my mind to help deal damage.
Melee Charmer wants powers that gives them buffs that help, some buffs are balanced by only being for one turn like Blur but can be doubled. some power that can be used and abused are things like Eviscerate, Savage Strike/Fury Strike, any power that can grant Obscured, Shielding Smite, Venom Strike, Night Shroud, Take Cover, Unbreakable, Hornet Blade, Sneak Attack and any other buffing power. Keeping Kiyoko makes her hard to slot but Kami-no-Michi or Onmyodo could work with Vestal Cait to tank and heal. Blue Flame Blade is assumed to be ran for the extra damage in all sets other then with Sneak Attack, Charge weapon can also be used but your picking fox for a reason.
Magic charmer can also work due to some spells giving buffs that can be abused too