What am I supposed to do when approaching Starscourge Radahn?

When he’s charging the purple arrow, you can’t get on your horse cause you can’t dodge it. Cool whatever.

When he fires the arrows in the air, you are forced to get on your horse. Then the spread shots come out, and it’s all rng if it hits you or not, cause the spread is random. Your horse dies, you get knocked off, you die cause of the rain of arrows. Am I just supposed to pray to not get hit while approaching him? I can run straight left or right and still get hit. Not only that but if he shoots the purple arrow you are guaranteed to get hit by it cause you don’t have enough time to get off your horse and roll.

Like, approaching him just feels like luck to not get hit, am I missing something?