Civimail 4.6.2 on Drupal 7.36 creating multiple drafts while editing
The answer is to update to 4.6.3. 

In CiviCRM 4.6.2 on Joomla 3.4.1, I experienced somewhat the same thing. After sending the mailing, the draft remained in Drafts and was marked as Completed with all the appropriate reports. So, there are two identical listings for the same mailing in each Scheduled/Sent and Drafts areas. 

Can the duplicate in Drafts be deleted or is it a the same entry as what is in the Scheduled/Sent area?  

I updated today with CiviCRM 4.6.3, and performed the same and usual process and this doesn't occur any longer.