Slow when using AirVPN DNS

[Megalith 1]

I'm using the Viscosity client. Checking "Apply DNS simultaneously" makes my connection use AirVPN's DNS (10.4.0.1) and prevents any DNS leaks. Unfortunately, my connection seems much slower when I'm using AirVPN's DNS. When I first connect, it takes a while for any sites to even load.

 

Do you think I have something configured incorrectly, or is this just the way it is? My connection seems to be fine when I'm using OpenDNS, but that leaks a ton of addresses (though I'm not sure if that even matters, since it's not my ISP's DNS). I also believe this problem only began when I switched to Windows 10; I heard that it might handle DNS settings differently.