Hi Roc
the drivers aggregation we know about is with multiple FireWire drivers. For Logic drivers aggregation with USB devices you should refer to Logic manual and Apple support or the various dedicated forums.
Once the H8000FW is properly configured, you can load or build a parallel routing for the 2 DSPs and have Logic Aux Sends configured to send audio tracks back and forth to the H8000FW for processing, exactly like you would do on an analog mixing board.
The H8000FW as a good Logic configuration example on its user manual.
best
I
