For those VIAF records which are linked to Wikipedia articles, VIAF reliably includes dates of death.
In my experience, one of the most reliably-added pieces of information in Wikipedia biographies is death dates.
You say "usually," but I see "occasionally." As an example, here's the LC authority record for me: http://id.loc.gov/authorities/names/n89613425.marcxml.xml, and if you can find "other important contextual information" you are a better reader than I am. Plus, when that information is available it's in a note field and can be quite cryptic:LC records may be lacking explicit (especially death) dates, but they usually contain a wealth of textual references which more often than not reveal exact birth dates and other important contextual information (affiliations, notable works, places of birth, death and activity).
-- Karen Coyle [log in to unmask] http://kcoyle.net m: +1-510-435-8234 skype: kcoylenet/+1-510-984-3600