The Witcher worked. I thought it was really good, but you could really tell where they had budget constraints. It was also carried by some decent actors, especially Henry Cavill. The Witcher universe is primarily humans as well.
Budget constraints such as, the dragon(s), and the final battle, costumes, etc.
An FFXIV live action series would have to have great casting, and like I said a massive budget. There would be no way to bring some of the fantasy creatures, and the like alive without it. I do not see it pulling it off. Things like player races would look ridiculous as well, unless they showed primarily Hyur. Roe, lalafell, etc. would look awkward at best on screen. That is unless they altered these race's designs for the screen. Disney Star Wars works with a multitude of races, but Disney is also Disney.