How Do I setup a Mac to bind to a domain automatically using DEP?

A machine can always be joined to AD as part of a regular policy, but of course, it would need to happen when the Mac is in range of your domain controllers to work. It can be scripted, or you can use a JSS binding object with your settings in it.
While I'm not using DEP yet, my understanding is this would all need to happen after the Mac enrolls into your JSS, meaning after the user sets up a local account and such. Hence one of the reasons why we are not using DEP. We're required to have clients use cached AD mobile accounts, but there is no way currently to do that with DEP other than after they have gone thru the DEP process and set up a local account.

We did this via PreStage Imaging. The settings only install a couple of apps, join to the domain, and assign printers. Since you are not having your end users use local accounts this might work. Our workflow is to do a first boot of the mac, set up the local admin account, and run Casper Imaging.

MikeV, Do you mean this is done during the pre-stage enrollment?

jamest, PreStage Enrollments do just that, enroll the device in your JSS during the initial startup. Once it's enrolled you can then use a Configuration Profile if all you want to do is join to the device to the domain.