First thing to note is that life will be a lot more painless if you specify home-specific DNS entries for different physical nodes - it makes supporting the system much easier. Curerntly, if 184.108.40.206 fails, then any requests to www.example.si should still succeeed.
According to RFC1123, the order in which records are specified should reflect the order in which they are sent to the client - and the client should try them in that order - however this has been superceded by RFC 1794. Certainly, for as long as I am aware, bind (and possibly other DNS servers) return equivalent records in a random order (unless explicitly told not to in bind 9.2.3 or later). For anything other than MX records, there is not "primary".
If, using nslookup, your DNS server is consistently returning records in the same order, then its time to have a long hard look at your DNS server config.