I forgot to mention, I read some interesting things on this page:
http://www.dokuwiki.org/ja:auth:ldap
Statements like "Support hierarchical groups, i.e. when a group is a member of another group. Currently only the groups user directly belongs to are detected."
I guess, on further consideration, I'm not dealing with hierarchical groups (ie no groups being members of other groups), but the notion of group depth is what piqued my interest.
It also references creating a "function auth_ldap_getGroups" in ldap.class.php, which I don't seem to have... yet on 2008-02-19 there was a statement that "This has been added for the new upcoming release".
That was almost 2 years ago... off the top of my head, I think there have been at least 3 official dokuwiki releases since that timestamp... so if this ldap group functionality was implemented, it is in a form different than what is being talked about on that page.
Makes me wonder if they were chasing after the same bit of functionality I am trying to use.