It should be clear for users (admins and non admins) why a revision was deleted when they view history of a page, e.g the reason for deletion of the revision (which appear in log) should also appear in history of the page near the deleted revision.

For example if in [[Special:Log/delete]] there is entry like:
*U changed visibility of a revision on page P content hidden ( Grossly insulting material)
Then in history of P this revision showed appear as deleted with the comment for deletion "Grossly insulting material".