It's interesting what the flux changes have done.
Previously the Storm Needler was a go-to weapon - comparatively short-ranged, but worthwhile as a large mount machine-gun equivalent, and was something I tried to mount at least one of whenever I was setting up an Onslaught or Conquest. Meanwhile, the Mjolnir was something you could only rarely justify using.
Now I prefer Mjolnirs; they've got the same efficiency as the new Storm Needler, much better anti-armor performance, and much longer range.
Gauss Cannons, by contrast, now fit into the same category that I think the Tachyon Lance ought to: great for keeping up long range pressure, but too flux-intensive to let them keep running if something gets in range of the rest of your guns. I use them, but it's a constant dance to decide when they should be firing and when they should be not firing. (TL *would* fit into the same category if, say, you doubled its damage output and flux generation...)
I actually wish I could replace the Onslaught's TPCs with Gauss Cannons; their old advantage of infinite ammo is gone, and they're significantly less accurate than regular hardpoint weapons were, back when the Onslaught had regular hardpoints up front.