This game's DLC suffers from the same difficulty curse that many other DLCs for other games suffer from, in that they are harder than the base game. For people who've played The Witcher 3 with all DLCs on, you may remember that if you decided to do Hearts of Stone and Blood & Wine first, before finishing up the main game, the Wild Hunt was a pushover when you were at level 60 (as the base game was supposed to be finished when you were at about level 40). It destroys the immersion in a way, as a vampire from Blood & Wine is stronger than the leader of the Wild Hunt, who are essentially trying to destroy the world.
Same deal with HZD, if you decide to do the DLC first then the final boss of the main game is easy. Yet you're kind of supposed to do it this way, as if you complete the DLC first you get some companions from the DLC for the end battle of the base game. Such weird choices sometimes.
HZD was a great game (it was a learning curve) and I am hoping for HZD 2 to be announced soon.