When you view only the epics, you should have the option to move the initiatives with that epic above or below another epic. Currently you have to go the initiatives screen and move them one by one if the epic order changes.
Currently if you change the order of the epics, nothing really happens to the order.

A bulk select and move of the epic and all children would solve this problem, however I understand that this is not always the required action, but there should be a way to say that I want to bulk move items.