Logged a bug:
Bug 17373236 - LDAP - DOES NOT REACH FAILOVER/LOADBALANCED SECOND ADDRESS
You can bypass this by using advanced url syntax:
You can use advanced url to use the syntax
There is thick/oci syntax as well(from an old post - requires additional oracle client install)
I found a related issue:.
Bug 14761950 - ADVANCED THIN URL FAILS WITH OCI CHECKBOX ON
Is this your issue:
with ldap entry with two host names (for failover):
-with oci switch on -> only tries first one
-with oci switch off (i.e. it uses thin) -> tries both
This would confirm the bugs are related, and provide you with a workaround.