I did see another similar question but I decided to start a new thread any way.
We use DNS Round Robin (multiple IP A records for the same host name). Every time a client does a DNS lookup they get multiple IP addresses returned in random order (this is a feature of DNS). The client (e.g. Chrome, Firefox, Safari, etc) will try the first IP in the order they were provided when it makes its HTTP request; most popular web clients will fail over (even in subsequent requests) to the other IP addresses DNS gave it if it doesn't get a response.
This is not dissimilar to many load balancing scenarios. DNS may only give you one IP, but a front end service often proxy's or tunnels the connection to one of many possible back ends. Although there are other sensor types monitoring as many CIs on all devices as we can, it would be nice to get an HTTP 200 from each web server that hosts a copy of the website.
Story: As a System Administrator using PRTG to monitor my hosting infrastructure, I want to have one or many sensors tell me the status of each instance of my load balanced websites, so I can easily see the health of that one endpoint and can address accordingly.
cUrl and even Powershell/C# should have ways to do this, basically we are either wanting to bypass DNS (specify IP address to send the HTTP GET request) and hopfully (even if later) in the case of DNS Round Robin, use it more effectively and check all IPs returned.
If it gets in your backlog, I would be happy to provide as much input as you like.