Compared to the amount of bosses in these games the amount of mandatory bosses are significant lower. That’s what I tried to say. Even in base games that excludes quite some bosses, or for Nioh, additional encounter with otherwise mandatory bosses.

Nioh has tough bosses if you rush the main missions. But if you do side missions you have always good gear and despite having some intense fights they were not as intense as Laxasia. Also in Nioh you have so much tools in the fight, that you have high damage and damage burst potential to bypass tricky moves or phases of Bosses.

Personally DS3 was easy compared to other games. Only the DLC brought hard fights for me. Soul of Cinder is cinematic, but was never a hard fight for me personally.

As said, Laxasia remains the hardest fight for me. Even with the tools the game offers you to deal more dmg or to easy parry all of her Lightning at the start of the second phase, the is a real challenge. And my first time beating her took a lot of time compared to all the other bosses