If the deep zoom image is blurry, it seems like you must not be getting the high resolution tiles downloaded to the browser.
Are you setting the "Scale" in Export to 100%
Are you viewing the result locally off of your hard drive, or over the internet?
Try clicking "Deep Zoom settings ..." and selecting "Viewer: HD View SL", this will force the Silverlight viewer and let us know if the issue is the viewer or ICE.