Even the MSQ doesn't have full voice acting, it's clearly something they still have to ration out which is unsurprising given the amount of text and the fact the game supports 6 languages (Chinese and Korean versions are also voiced). The amount of VO has increased every expansion. I do appreciate them sparing the effort to do voices for raid bosses and for an important scene outside the MSQ and would certainly like to see more but VO will always be a constraint, I think.