A couple of points:
- If you're on the latest version, there's a known issue with Openfire 3.9.3 and LDAP groups. It is filed as https://igniterealtime.org/issues/images/icons/bug.gif OF-830. Openfire 3.9.2 seems to not have this issue.
- The "Share group with additional users" box should only be used if you want users that are *not* members of a group to see it in their client. If you have a Spark group with all your users in it, there's no need to check that box. If LDAP is set up correctly, then all the users in that group should see it in their client with just the "Enable contact list group sharing" option. That's how it works for my system, at any rate.