2 sword 2 down crota hard:
https://youtu.be/2CeAoBDwP1A
Just my way of doing it
Using super dash in air then use vanish before picking up sword to save time from going to rock and kneeling
Call for rockets as soon as you jump onto Crota platform
Always looking at Crota and seeing his health bar to know when to start using sword. Note for people who don't know his shield is the white health bar above the yellow one.
The combo in the video is
R1 r2 r2 r2 r2
Drop sword blink strike
R1 r2 r2 r2 r2