Myoshu doesn't give +10 Subtle Blow, it enhances the effect by 10% (this can go over the cap.) You're left at 35/50 Subtle Blow without Auspice, which is quite a common situation. Honestly I might be slightly better off using Iga Erimaki and some hands that give +Haste when I do have Auspice, I just dislike how unsightly all of the other choices are.