so, slight adjustment, 2x banettes
1st banette
-MUST get first-strike with from claw with will-o-wisp(burn cuts physical attacks by 1/2, and he only has physical attacks)
-He cures it immediately with full-heal, you keep casting will-o-wisp till he runs out(full-heal clears burn before you hit again with will-o-wisp to reapply the burn)
-Eventually die after he runs out of full-restores, youre not going to hit before him, so keep spamming will-o-wisp for good measure
2nd banette
-Use curse, as long as hes still got burn, you have high chance of surviving a single hit, and applying curse(it will faint your mon, but 1/4 maxhp/turn against a vastly OP mon is worth)
Shiinotic
-Use strength sap, itll outheal his hits every turn, and he only has 4-5 turns left before curse kills him
you dont have to worry about PP running out with the second banette casting a curse if your S.ATK is too low, just need enough HP/Def to tank his first strike each turn
3 mons, 3 moves, no items, and its a done deal in all of 10 rounds
if youre grinding 2x mons for this fight, 3x shouldnt be a big deal, and assuming you abuse technician-meowths payday as much as i do, affording a Power Weight(held item: +hp ev) and Power Belt(held item: +def ev) should be relatively trivial to-dos