I always felt that W3 had some aspects of the 'hero's journey' story structure, concluding the path that started with the books. Geralt's journey is much longer and more complicated (a 400 hour story in total) than a traditional hero's journey. He goes through all steps in the cycle, often many times throughout his quests.
And in the later stages, many parts of Witcher 3 main game and more obviously the entire Hearts of Stone expansion is the Apotheosis of Geralt. In Hearts of Stone one can see how much Geralt has grown. It's like a giant test as if the many tests in the W3 weren't enough. Then he gets his 'final labor' in Blood and Wine and retires. A lot of the elements of Blood and Wine are similar to the later stages of the hero's journey:
Hero's journey - Wikipedia
The Writer's Journey, 2nd Edition (enthuz.com)
Geralt experiences all of these things in the two expansions (and even in the fan-made tribute, Farewell to the White Wolf). What I find remarkable about the writing and quests is that these aspects are really subtle. I didn't pick up on them in the first time through but I sense that they were there. It's like they are there but naturally, organically. The writers weren't hitting players over the head with their ideas. Really brilliant.
Apotheosis
This is the point of realization in which a greater understanding is achieved. Armed with this new knowledge and perception, the hero is resolved and ready for the more difficult part of the adventure.
Atonement with the Father/Abyss
In this step, the hero must confront and be initiated by whatever holds the ultimate power in their life. In many myths and stories, this is the father or a father figure who has life and death power. This is the center point of the journey. All the previous steps have been moving into this place, all that follow will move out from it. Although this step is most frequently symbolized by an encounter with a male entity, it does not have to be a male—just someone or something with incredible power.
The Ultimate Boon
The ultimate boon is the achievement of the goal of the quest. It is what the hero went on the journey to get. All the previous steps serve to prepare and purify the hero for this step since in many myths the boon is something transcendent like the elixir of life itself.
Refusal of the Return
Having found bliss and enlightenment in the other world, the hero may not want to return to the ordinary world to bestow the boon onto their fellow beings.
The Magic Flight
If the hero in his triumph wins the blessing of the goddess or the god and is then explicitly commissioned to return to the world with some elixir for the restoration of society, the final stage of his adventure is supported by all the powers of his supernatural patron. On the other hand, if the trophy has been attained against the opposition of its guardian, or if the hero's wish to return to the world has been resented by the gods or demons, then the last stage of the mythological round becomes a lively, often comical, pursuit. This flight may be complicated by marvels of magical obstruction and evasion.
The Crossing of the Return Threshold
"The returning hero, to complete his adventure, must survive the impact of the world." The goal of the return is to retain the wisdom gained on the quest and to integrate it into society.
Master of the Two Worlds
For a human hero, it may mean achieving a balance between the material and spiritual. The person has become comfortable and competent in both the inner and outer worlds.
The individual, through prolonged psychological disciplines, gives up completely all attachment to his personal limitations, idiosyncrasies, hopes and fears, no longer resists the self-annihilation that is prerequisite to rebirth in the realization of truth, and so becomes ripe, at last, for the great atonement. His personal ambitions being totally dissolved, he no longer tries to live but willingly relaxes to whatever may come to pass in him; he becomes, that is to say, an anonymity.
Freedom to Live
In this step, mastery leads to freedom from the fear of death, which in turn is the freedom to live. This is sometimes referred to as living in the moment, neither anticipating the future nor regretting the past.