Also as to races the ISA have trouble with in my experience, the big 2 boogeymen are the Drakh and the Shadows. Why? Dodge. The bulk of the ISA fleet are basically Whitestar varients, and despite all their fancy gadgets and traits, whitestars are actually quite fragile when they take hits, fortunately for them they all have dodge to some degree so can avoid alot of hits.
Shadows have the Shadow scout, which is potentially FASTER than a whitestar, and can outmaneuver one if it needs to, and it has powerful weapons with the accurate trait that are pretty much tailor made to shred whitestars.
More or less the same thing can be said of the Drakh Light Raider. Its not AS nasty as the Shadow scout but then again, its generally far more numerous
Also, while whitestar weapons are advanced and potent they dont actually throw that many dice at a time and tend to rely more on chipping away at larger ships while avoiding return fire than that one massive alpha strike of some races bigger ships. This sort of attack is where Shields and GEGs are at their most effective.
So basically, Drakh, bad news for the ISA. Shadows, tradtionally, THE nightmare fleet for the ISA (at least for a WS heavy version, Victories in my experience work very well against shadows, but then Victories in my experience tend to work very well against ANYTHING if youve got enough other ships to back it up

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