How important do you think it is to have a wiki-level revision viewer, similar to the page revision viewer? The wiki revision viewer would show thing like page deletions to allow you to restore deleted pages. (I just added a confirmation dialog when deleting pages, by the way).
Currently you can restore deleted pages if you delete a page and then create a "new page" with the same name, but this is non-intuitive and worthless if you don't know the precise name of a deleted page. The page will be blank, but the history viewer will then show you all the previous revisions, including the event of the page deletion.