avatarResizer plugin replaces the default provider.vcard.className, but that your replacement appears to be missing a few things.
The end result of this is that vcards are not returned.
The reason it took me so long to realize this, is that if an openfire installation has a healthy vcard cache built up, that information is returned (and the picture is resized if present and the client doesn't already have it), thus it looks like everything works. But if the cache is cleared, vcards are not returned.
I have already tried the obvious things like:
reloading the plugin
verifying the information is still in LDAP
Switching provider.vcard.className back to the default immediately starts to return vcards as expected (just without the picture resizing).