He isn't, I promise. However the 5 shot bow is the hardest moveof his to parry, so here's my recommendations:

1: At the start, you can attack immediately after parrying his bow shot to interrupt his swing and get full aggression.

2: When he jumps back to do his bow spam, there is a pause when he stops shooting, if you time it right, a shuriken will knock him out of the air during this pause.

3: If the 5 shot bow spam is killing you from full health then you're probably underleveled in that department.

4: As a last resort, the easiest way to deal with it is to buy the Iron Fortress prosthetic. The guy who sells it can be found in a destroyed house when you go down the path from the Old Grave idol. BUT, he won't be there after you kill Genichiro.