I feel like if you can beat Gundyr you can at least struggle through the first part of the game. I agree the Road of Sacrifices to Farron Keep is pretty rough but it’s also pretty easy to run straight through. Even if you don’t know the way it’s not too convoluted. Once you reach Irithyll though it gets considerably harder, especially boss-wise. Pontiff is a nightmare if you can’t parry. Conversely, all the bosses before him are relatively straightforward, even if a little hard. But with a few attempts I don’t think it’s a severe challenge quite like Pontiff is. From that point on it’s pretty tough the rest of the way though, with a couple minor exceptions.

I’d say Midir and Gael are kind of like Kalameet and Artorias. Whichever you found harder in DS1 will probably carry over to DS3. I found Kalameet way harder, and I also find Midir way harder. Artorias, while challenging, was a lot easier to me, just like Gael. You can also challenge Gael without fighting Midir. Midir is completely optional, just like Kalameet.

If you haven’t already, you should give the ER DLC a try. It’s probably their best content to date. It’s definitely harder than the base game, but like the base game, you can cheese it if you need to. The only exception is the final boss, who is only really possible if you cheese it, and even then is tremendously difficult. But the rest of the DLC is a fair challenge and really fun.