The start with shifu is simple because it gives you skill speed + auto attack speed.Were not for the auto attack buff, yukikaze + jinpu first would give you more damage until you get all 3 together (yuki + jinpu + shifu).

The hagakure is 20 free sen for a shinten or kaiten since you re gonna use meikyo afterwards and , as a dps, you want to burn all of your off cooldowns asap to make it reset timer so you can use again since the fight has time limit.

If you open with yukikaze + higanbana you wont have enough sen for Kaiten + higanbana, forcing you to use in midare (which gives you a HUGE increase in dots, especially crits).