My problem with manual fire was that it's so tedious for how many enemies there were. Hm, when I think of something comparable, something like Diablo 2, I would click constantly, too, but it doesn't feel as exhausting. Can't really pin point.
Another thing: the perspective felt incredibly far zoomed out. I always had the urge to zoom in. At the same time, it was sometimes difficult to separate a wall from a walkable path, when it was all dark and narrow.