Technically the Shepherd class isn't even new but was a partially planned one for version 1.0, only to be never completed and was thus dummied out - it actually had a locked Guildhall in Falcon's Nest, which naturally no longer exists by the time of ARR/HW, and it even had a class icon (which matched the logo on the sign above the aforementioned Guildhall), as shown:


I have no idea where this logo came from, I found it on a FFXIV site that has since disappeared so anyone's guess is as good as mine.

As for how it works, I could speculate, but everyone else has come up with interesting ideas so I'll just leave it that hopefully SE will look into this, even despite all traces of it's 1.0 roots being abandoned.