It looks like it's working properly from what I can see. I remember now why you won't be able to add members manually to the user group, because it's linked to the external one it'll get refreshed after saving it.

It does look like it's found the group successfully:

2015-11-27 09:17:12 [ldap] [D] op search (7.1ms) [ filter=, base= ]
2015-11-27 09:17:12 [ldap] [D] op search (11.0ms) [ filter=(cn=grp_its_unix_adm), base=ou=groups,ou=unallocated,ou=MYCOMPANY,dc=MYCOMPANY,dc=edu,dc=au ]
2015-11-27 09:17:12 [ldap] [D] op search (147.4ms) [ filter=(cn=grp_its_unix_adm), base=ou=groups,ou=unallocated,ou=MYCOMPANY,dc=MYCOMPANY,dc=edu,dc=au ]
2015-11-27 09:17:12 [ldap] [D] op search (8.7ms) [ filter=(|(|(objectClass=posixGroup)(objectClass=organizationalunit))(objectClass=groupOfUniqueNames)), base=CN=grp_its_unix_adm,OU=Groups,OU=Unallocated,OU=MYCOMPANY,DC=MYCOMPANY,DC=edu,DC=au ]
2015-11-27 09:17:12 [ldap] [D] user_list (175.2ms) [ group=grp_its_unix_adm ]

It will iterate over member, ismemberof, memberof, memberuid and uniquemember attributes of the group so do check from an ldapsearch that it has some of those?

Also check that the login names in Foreman match the member names in LDAP. If it has those attributes, enabling the "sql" logger might also shed some further light as we ought to see queries in the users table.

Will keep trying to get as much information as possible. Additionally, is there any particular reason why users are not added when they log in with ldap (on-the-fly user creation enabled)?

I have created a fresh install of Katello in a new virtual for testing. Now I have encountered this after setting up the same ldap config: the only user I can see is the default admin. I log in with my ldap credentials and it works fine. When I go to the users section when logged in as admin, no users are created. But when I try to create an internal user manually with the same ldap username, I get a message saying the user already exists (even when it is not listed). Are users are not being displayed? Could this be a database access issue?

Perhaps due to orgs/locs, try changing context from the top-left hand menu.