Myos, please be patient. The drop rates have not changed.
In the cases you did not get a box (the 30%) it is most likely when you got a fortune box but because of the bug, it did not give you anything. Please update your app or restart your game and try again. It should be fixed.
Im not sure why you would be expecting an epic from a regular box (those are not guaranteed in the regular drop box) but if you meant fortune boxes, please read Sarah’s response thoroughly.