I have played more than 400 hours of Nioh 1 and the difficulty here seems the same, maybe even a bit more brutal but you have more tools at your disposal too.
That being said, I struggled way more with bosses in Nioh 1 so far, but that may just be because it was new at the time, while now it's familiar.
I think Hino-enma in Nioh was a real skill check boss that basically tested to make sure you could handle the game's mechanics. I was kind of fumbling my way through the game and just playing it as Loot Souls until everything clicked after I fought her 20 times.
I feel like Nioh 2 doesn't quite have the same early skill check. They throw a tough Yokai at you early to teach you Burst Counters, but I've fought the first 3 bosses and none of them really made me feel like I had to master the mechanics to move forward, which may be why the Nioh 2 bosses don't feel as difficult.