DNS round robin is not failover. If one of your four A records points to a dead box, 25% of your customers are SOL.
Browsers even try other IPs and alternate between IPv4 and IPv6 before the connection is established.
The whole point of it is to connect to multiple A and AAAA records with a very short delay (250ms in chrome). The browsers use poll to get notified about the first established connection and then use it. So if one A/AAAA records IP is unreachable or slow it will use a another one. There will be no fallout (except maybe for clients that don't use something like happy eyeballs, but any browser does that) if you have multiple A/AAAA records and one of them is down.