I have only played ds 4 so I can't answer your question if it's harder than the other versions but I can give my input on the difficulty. It's not to hard except for a couple of fights. I don't believe the game explains that undead are(maybe I'm just stupid) weak to healing magic/items so the fight with the undead fiend on the mountain is almost impossible if you try to attack him without healing magic. Next unfair fight is the fight with golbez's shadow dragon. Most of your party is useless or gimped since they can't wear or use anything metal so the fight is kinda up to luck. Next would be the fight with Golbez. You only have Rydia to revive the party which is an issue since Rydia is super weak due to her not being in the party for a few hours, luck based if you win. The entirety of the moon dungeons have enemies that are 10x harder than the final boss so it's best just to run. Not to hard expect for those few dungeons and bosses.