I have read a few threads stating how hard it is to react due to how fast his attack comes out, how little time you have after it shows what direction it is coming from, and how he is able to switch to any side during the start up.

I have noticed a design in the game that can help narrow down what direction he is going to attack from. (Im not sure if anyone else has noticed this)

If you listen to the animation sounds you can distinctly hear that orochi makes a specific sound when attacking from the top in storm rush.

Noticing the sound gives you plenty of time to move your guard to the top.

By knowing this you can shut that move down rather effectively because his top attack is his most useful due to the fact that it is unable to be dodged.

Take the time to listen and practice against him. I hope this helps those that have been struggling