Are you using any kind of automation software (ansible chef puppet etc?).
Atm I'use pssh and pscp for manage and send all the configurations scripts. But I've also a software able to do that.
Also one of the things that interested me in the Odroids is the ability to PXE boot them. Im a little surprised you hadn't done this, perhaps the HC1's dont support this?
Because I've really never looked into it tbh. And also because the PXE boot on those boards was introduced by hardkernel when i've actually finished buying/flashing/installing all the MicroSD.
How have you managed bad cards / bad boards?
I don't know, never got a bad one!