I´ve been reading the official thread on ResetEra and the vast majority there think it´s far harder than any Dark Souls game and Bloodborne, but of course difficulty is one of those things that might vary wildly depending on the player´s skill.
Might just be because you can't just level up and cheese the game, you have to ACTUALLY git gud. (I hate that phrase but it applies.)
My Console Library:
PS4, PS3, PS2, PS1, WiiU, Wii, GCN, N64 SNES, XBO, 360
3DS, DS, GBA, Vita, PSP, Android
Top 6 this generation:
Bloodborne, Sekiro: Shadows Die Twice, God of War, The Legend of Zelda: Breath of the Wild, Dark Souls III, Red Dead Redemption II, Rock Band 4