The "document request" strategy was obviously designed to provoke an extended dispute with the White House, and thereby to deny Miers a timely vote on the floor. Read Krauthammer's article: http://www.freerepublic.com/focus/f-news/1506622/posts
It worked --- You may not consider that this highjacking of the nomination was done in "broad daylight", but it certainly was clear to me, as well as others who read Krauthammer (who by the way wasn't the first to propose this underhanded method to scuttle the nomination). This method has been used to scuttle presidential nominees in the past, was tried as recently as with Roberts, but the Demodogs didn't get any Republican support in that instance, so it failed then, unlike with Miers.
The Dems were wrong to insist on such with Roberts, and it was no more right in the case of Miers.
You are correct that the document request was inappropriate. But it did NOT deny her a vote.