As VyOS 1.3-epa1 will be released shortly it's the last change to iron out some CLI design flaws from the past.
We have `set system name-server <ipv4|ipv4>` to specify a nameserver IP address we wan't to use. We also have `set system name-servers-dhcp <interface>` which does the same, but the name server in question is retrieved via DHCP.
Both CLI nodes should be merged under one `set system name-server <ipv4|ipv6|interface>` node - to keep things as they are in real life - we need a name-server.