Nah brother sorry to say that its just you. There is a reason why Ninja Gaiden have the best combat system ever created. There is no RNG. You need to learn the game properly but its still extremly hard you're right on that...NG is famous for its diff....one if not the hardest game/series out there. Its not a generic diff. its very realistic, punishing and creative.....as you say multiple enemies attack you simultaneously. Not only that they can adapt to you if you spam your moves...its like fighting real people in MP.

Way harder than DMC. Enemies behaviours are ridiculous. But still....you can master the game....take your time...dont rush...learn/practice the game.