This bug is created as a clone of upstream ticket:
https://fedorahosted.org/sssd/ticket/2418

sssd code includes hard coded values for AD DC os version:

https://git.fedorahosted.org/cgit/sssd.git/tree/src/providers/ldap/sdap.c

{{{
if (ret == EOK) {
	/* Validate that the DC level matches an expected value */
	switch(dc_level) {
	case DS_BEHAVIOR_WIN2000:
	case DS_BEHAVIOR_WIN2003:
	case DS_BEHAVIOR_WIN2008:
	case DS_BEHAVIOR_WIN2008R2:
	case DS_BEHAVIOR_WIN2012:
		opts->dc_functional_level = dc_level;
		DEBUG(SSSDBG_CONF_SETTINGS,
			  "Setting AD compatibility level to [%d]\n",
			   opts->dc_functional_level);
		break;
	default:
		DEBUG(SSSDBG_MINOR_FAILURE,
			  "Received invalid value for AD compatibility level. "
			   "Continuing without AD performance enhancements\n");
	}
} else if (ret != ENOENT) {
	DEBUG(SSSDBG_MINOR_FAILURE,
		  "Error detecting Active Directory compatibility level "
		   "(%s). Continuing without AD performance enhancements\n",
		   strerror(ret));
}
}}}

https://git.fedorahosted.org/cgit/sssd.git/tree/src/providers/ldap/sdap.h

{{{
/* Values from
 * http://msdn.microsoft.com/en-us/library/cc223272%28v=prot.13%29.aspx
 */
enum dc_functional_level {
    DS_BEHAVIOR_WIN2000 = 0,
    DS_BEHAVIOR_WIN2003 = 2,
    DS_BEHAVIOR_WIN2008 = 3,
    DS_BEHAVIOR_WIN2008R2 = 4,
    DS_BEHAVIOR_WIN2012 = 5
};
}}}

There is a new OS version avalable in:
http://msdn.microsoft.com/en-us/library/cc223272%28v=prot.13%29.aspx
6 = DS_BEHAVIOR_WIN2012R2

This means sssd cant authenticate agains Win2012R2 server AD DC-s.