How to cite an updated report?
I think the main problem here is the use of the term "published" just because it is posted on the web page. If a report is under revision, it is strictly speaking not published. Once published it should be fixed in terms of its content or it should carry some form of revision marking such as "Second Edition" or "version 2" in which case the different editions or versions must be continually available. 

If you find some information in the 2013 draft which is later dropped, it means the authors no longer support that point for one or another reason. Hence it would be potentially bad to attribute such a point the authors.

So from this perspective I do not support any of your forms for referencing. It appears you should view the work as unpublished and only rely on the latest version as a source for information.