I'm not aware of an existing utility for automatically posting a HTML help file to Deki Wiki, although it would be very useful. You could create one using Deki Wiki API to automatically generate pages and post content to them:
See these threads for more information on using the POST content API: http://forums.opengarden.org/showthread.php?t=342 and http://forums.opengarden.org/showthread.php?t=1061.
curl -c cookies.txt http://username:password@deki-hayes/@api/deki/users/authenticate
curl -b cookies.txt -d @test.html -H "Content-type: text/plain" "http://deki-hayes/@api/deki/pages/=pagename/contents"
If you do decide to write such a script, please let us know and we'd love to share it with the community!