In Plesk, when you add domains, it lets you specify the Nameservers for that domain. What's the point of that?
For a domain, aren't the only nameserver settings that matter the ones at the domain's registrar?

They need to be in the zone file too.

If you have 4 nameservers and only two in the zone, sometimes it will only use the two.

What you are saying is right, but yes, i remember awhile back they were absolutely necessary to be in the zone - not sure now

Good help aren't i?!

NS records are used to delegate authority, so the NS records for your domain should match those that are listed at your registrar, otherwise, some things might not work right. As per RFC guidelines, BIND 9.x will reject zones without at least one NS record.