Right now, I think an effective Nebula build replaces the old GW1/PSW3 duo with VM1/TR3. Due to the completely broken mechanics of drains in this game, if you can proc the rift multiple times, then it will keep stacking. So, when you can proc 4 rifts of -14 power to all systems, you can demolish the power systems of anyone. VM1 is just there to provide backup, and you can always drop in a GW1 instead. I was running GW1/TR3 with no doffs to enhance either one (didn't feel like dropping the EC for a TR doff) in my torpedo nebula, but I haven't booted up the game in almost two weeks.
I don't advise anyone running mines, but that's personal preference; however, if you want a debuffing torpedo, I would say run chronitons over tricobalt. If you can run the photonic shockwave torp, then that plus two chronitons would be rather effective at keeping NPCs slowed, no?