Seems that there's a problem with the max output of the fission controller.
Tested with: Draconic Basic I/O Crytsal, Ender I/O Conduits and infinite Flux Ducts from Thermal Expansion.
Output of Fission Controller should be 196K RF/t. Output still 120K Rf/t. Rest of it lands in the internal storage of the controller.

Found the mistake - will get it fixed shortly... it's quite late here so it will probs be tomorrow :)

Ok, should be fixed in 2.8c :)