I don't consider the Heavy Blaster imbalanced: its flux cost is insane and very few ships can sustain it for long. It is powerful but you're paying an exorbitant amount of flux for it. For it to be imbalanced would mean that the pros vastly outweigh the cons, and that is not the case.
The Plasma Cannon, on the other hand, is a Heavy Blaster on steroids with better range, equal armor penetrating power, and much higher efficiency. It's only 15% more expensive flux-wise than the Heavy Blaster but it's 50% more powerful. It's only downside is its 30 OP cost and rarity. In terms of flux profile, it's relatively efficient for something that hits so insanely hard. Yet, I still don't think it's "imbalanced" because its still hard to sustain and the cost is so high.
The Assault Chaingun is really the only outlier, to me. When it was 400 DPS for 400 flux, it was powerful but expensive. Now that it's 600 DPS, it's brutally efficient. Its downside is its range but once it gets into range, it murders armor. I used to use the ACG as an example of "bad against armor" because it's damage/shot was so low but since it got bumped up 50%, it outshines even true armor busters. Yet, at the same time, I'm glad that the weapon exists because it does give knife-fighting some teeth. Personally, I'd prefer the ACG go back down to 400 DPS but just reduce the flux cost to 267 flux/sec. Same efficiency ratio but the DPS wouldn't be as insane.