for each [WinEventLog: ] stanza in inputs.conf, can you specify more than one entry for evt_dc_name? Because what if one of the DCs goes down? Same question in relation to setting up LDAP authentication - can you specify more than one host/DC in the authentication.conf file, for redundancy?
No you can not, but you can specify a DNS name that might point to a load-balanced/failover set of AD/LDAP servers.
For example, AD domains are often set up such that the AD domain domainname.company.com resolves to list of available DCs for that domain.