I found the mistlands a challenge but doable as a solo player but I only arrived there after the nerf hit. I would say it's a bit less difficult than arriving to the swamp for the first time but I also overprepare a lot. There are some new items which help a lot with the biome so once you get them, mistlands seems pretty manageable, even as a solo player. 2 star enemies in dungeons were a nightmare for me in the beginning, though.