I had read reports from several people (including the comments here) that this bow doesn't drop. I decided to test that by running this task over and over. Well after ten cycles, I've received 0 bows. Given that Mujaki the Devourer drops 2 of his loots per death and only has 3 other loots on his table, it would be be incredibly unlikely that I just simply got unlucky. In fact assuming each drop has an equal chance of dropping, my bad luck would be 1/315!
So I for one am considering this a bow as one that no longer drops, and not including it in my bow collection. I wouldn't recommend others to try to get it!