When dragging an item in the visual editor (tested with image and text), the editing window does not scroll up or down when you reach the top or bottom of the window. This means you have to make several consecutive drag and drop actions to move an item within a long article/section. Per Bug 51665 the image must be separately selected before you are able to drag it (i.e. each movement requires two mouse clicks).
See Also:
T36307: Page doesn't scroll when dragging selection off bottom of window in VisualEditor
T75240: VisualEditor: Drag-and-drop in IE9 doesn't work