Zach McGowan would have made for a perfect Geralt imo, the acting, the voice, his physique, much more in line with Geralt (both Book Geralt and game).
To me it seems like that the showrunner had already decided on Henry before they even started auditions and casting because Henry had talked about it before then. Of course Henry is a much bigger name then Zach so once he showed interest it was probably an easy get for Netflix coming off of MI/Superman, but to me he just doesn't look/feel like Geralt, he's not lanky, doesn't have the gruff voice and acting wise he's not as good imo, at least when it comes to playing that kind of character.
I still hope it turns out good, and they certainly are trying.