+1. I was never OS X Server certified or anything, but the certified guy who got me up to speed at my first OS X Server related job stressed DNS super hard. Over the years, I helped troubleshoot Open Directory issues for several organizations — nearly every time, it was because they were using an IP instead of an FQDN, forward lookup zones weren't set up correctly, or reverse lookup zones weren't set up correctly. No error messages; client Macs would just refuse to authenticate at the loginwindow.FWIW, when I did my OS X Server training/certification at Apple (many moons ago) DNS was considered mandatory. Also, as a consultant I had a handful of service calls where setting up DNS resolved random login issues.
OD / Network Homes / Mobile Accounts are all tricky and fickle beasts, IMO... Cool in their day, but constant trouble.