The Wyrm God - Shinryu - Drop rate issue

Hello Square Enix team, I'd like to give you some feedback on the fight. After nearly 200 fights on VD difficulty with a consistent TH (9 minimal), we haven't received a single significant drop, such as Crepuscular Knife, Crepuscular Helm, Crepuscular Cloak or Crepuscular Mail.
This is beyond frustrating, and we'd like to know the drop rate because we're extremely discouraged.

Thank you in advance for your reply.

very likely 0.2% for each item you listed as well as Crepuscular Scythe.
Not seeing a drop in 200~400 VD runs is probably not too unlikely.