First, I tried the butt Reaper loadout, but it is awkward to use, and only two or three shots.
Next, I tried AMB loadout. Even with Systems Expertise, it took longer for it to recharge than AMBs to reload. Any other energy weapon to strike after QD was pointless.
Finally, I tried an armor tank with three Heavy Blasters, and it smashed enemy destroyers. After that, I replaced the blasters with phase lances and added Hard Flux Scatter for hard flux lances. Harbinger can kill things of its class fast. Only problem? I did not need Quantum Disruptor for brawling at all. The system is minor when the opening is brief, and the damage Harbinger can do in a salvo is relatively minor. My ship might as well have had no ship system.
Either Quantum Disruptor delay should be shorter (30 seconds is too long. Even System Expertise did not help enough.), or Harbinger should get a different system. With three energy mounts, I would rather have High Energy Focus instead of QD on Harbinger, or better yet, swap Afflictor's and Harbinger's systems back to what they were several releases ago, with Afflictor having (today's) QD, and Harbinger having ED.