Migrate DNS & Cluster to new server(s) - How to best achieve?

Hi,

So, I've got a slightly weird scenario and would like to know what you think of it:

Right now, a CPanel server (let's call it Server A) has a given IP address as main address and is in a cluster. Server B and Server C is in the cluster.

The IP addresses of server A & server B are also declared in GLUE records for domain names ( of the type ns1.something.com) - server C is not, it's just part of the cluster.

What's the issue here - I want to make DNS independent of server A, because I plan to stop using server A soon.

How would this be most effectively achieved, I wonder?

Here's what I thought:

Have server A "take server C's place" i.e. belong in the cluster, but being removed from GLUE records in domain names.

Then, from the current status where it's:

ns1 in GLUE - Server A
ns2 in GLUE - Server B
(server C in cluster but not in GLUE)
We'd have:

ns1 in GLUE - Server B
ns2 in GLUE - Server C
(server A in cluster but not in GLUE)

But is this the right way to do this? Or should I, perhaps, disable DNS on server A entirely and have DNS served only by servers B and C?

Furthermore, if what I'm describing can work, should I delete the current cluster and re-make a new one at Server B? I've noticed that the primary server performs better (?) sync with other cluster members, i.e. if I say, add a new account at Server B at the moment (which is secondary in the cluster) it may not necessarily sync to Server A until I run "Syncronize DNS to all servers".

Any advise on the best practices to follow re: the above will be most welcome!

Thanks!