The browser does not try another IP if the request fails; it tries the first one only (the DNS server chooses a random order for the response), unless browsers have changed their behavior recently.
DNS round robin is not failover. If one of your four A records points to a dead box, 25% of your customers are SOL.
DNS round robin is not failover. If one of your four A records points to a dead box, 25% of your customers are SOL.