during the beta days, before batch rendering was possible in octane, I wrote a program to batch render multiple octane files. One of the features I had that I realize is missing is the ability to assign cards to batch job nodes.
A lot of times with in the past, I'll dedicate one card to working in octane while my batch program was dedicating the other 2 for it's processes. It made for really smooth operation without having to think about turning on or off cards in multiple instances of octane.
Basically, adding a node to the batch job node (gpu's used or whatever) and it would override whatever the settings are in octane.