A better idea than messing about with hosts files to prevent connection to the individual server that’s got the problem would be for us to identify which servers in the farm are experiencing the problem. You can do this with the standard administrative tools that come with Windows 10.
Windows 10 → Start → Windows Administrative Tools → Resource Monitor
This will start you in the Overview tab of the Resource Monitor
In the Processes with Network Activity section, left-click the column title image to sort it alphabetically
Scroll down until you find Diablo III64.EXE and tick the box to its left
This will now put it to the top of the column
Now click the Network tab and you should see something like this…
Now, choose your hero and start a game. This will cause the client to select one of the available servers in the farm for your game to be hosted on. Once your hero is in-game, alt tab back to Resource Monitor and you’ll see an extra connection, like this…
Make a note of the server IP address your game was hosted on and whether you had good or bad latency. Compile a list of known-good and known-bad server IPs, and post it here. That way Blizzard’s technicians know which of the servers in the farm are experiencing problems and hopefully they can address it for all the players, rather than individual players trying to avoid the problem servers by messing with their HOSTS file.