For users who use multi-site and found the url redirects on logout don’t work, here’s the solution I found today. It involved a little digging into the mu-plugins directory and a small addition to the code, but it’s not too hard.
It involves editing domain_mapping.php and adding the two lines immediately after the comment (and before the echo statement):
This is not my solution, I originally scored this little tidbit from the wordpress support forums. The original appears here. Posted here for reference.