I'm in the S&D discord and was pleasantly surprised to see the guy who does cool modding stuff uploading videos. Binged all these runs, very awesome :) Glad to see someone appreciates the bustedness that is Scorpion's Tail. Really good into every boss fight except Inevitable (it's like, fine turn 1 to prevent an exert but usually not worth the pain in that case). As for Ninja, I think the ideal strat if you're forced into her is to treat her like Gambler unless you have a synergy (Managain, Bloodlust, Steel). Putting a side replacer on her will often be more value than a 1 damage copycat.
Never knew people were hating on scorpion tale, I find it busted for negating all the scary summon and Aoe attacks. Dragon and Hand are just complete jokes with it.