Retribution is always gonna be overfluxed, it's got too much dakka not to be.
Instead of dual flaks, you could use regular flaks. 1/3rd the flux per second, +100 range, and more damage per shot (more important at the ranges retribution engages at imo). You don't really need the fire rate of the dual flaks when you have multiple regular flaks, especially if you supplment it with some vulcans. Or use devastators for PD+anti armor/hull lol.
Build I do for piloting retirbution is 2x devastator, 1 storm needler, and a bunch of machine guns. Mediums can be mining blasters or mortars. Needs elite PD though if you don't want to have to stand directly in front of the enemy to kill them.