On a CIFS/SMB domain the WINS service is critical for proper function [some things use WINS, some things use DNS, it is terribly confusing, but it is what it is]. DNS is relatively easy to test and you will likely know right away if it isn't working. But before adding those new DCs to your dhcpd.conf file -
option netbios-name-servers 192.168.1.78, 192.168.1.79, 192.168.1.65;
... it would be nice to be equally confident WINS is operating as expected.