Administration block wastes whole column. Well, the whole of the column below the block itself. Moodle isn't that long on width real estate as it is and to have a block-width of empty space on the right is a but of a waste. Is there any way of either hiding it maybe conditionally on editing on/off or banishing it to the footer or the header?
Can you post a screenshot? Is this a custom theme you have?
You could dock it, or you could use a theme with a variety of block-regions and the admin block can be set to appear in any of them.