I enjoyed the movie quite a bit, and at least our local showing I went to was quite packed. But obviously overall that wasn't the norm. What really was surprising was that so few wow players went, and virtually no non-wow players went to see it in the West. Obviously it was much better marketed and had a wider audience than just wow gamers in the East.
As for the movie, I read the books and follow the lore so it all made sense to me. But I could see where even wow players who don't read quest text could have been lost. The casting was ok except for Khadgar and Medivh who left something to be desired. There were also some scenes cut from what I understand to keep the movie from being too long, and that likely added to confusion for viewers that didn't know the lore well.
I'm hoping for a sequel but I'd understand based how badly it did in the West if they don't. It would be even crazier if they did an only-Chinese version of a sequel.