I have a fairly rigid fleet organisation and tactical structure, which I really ought to be hit harder for, and the fact that I'm not really does indicate there might be a problem.
I don't believe the scissors, paper, stone argument- it's not that straightforward, bad fleet selection can make you lose to anybody. I do believe there is a sort of upper and lower division situation, one group of races whose success or failure against each other is largely determined by tactics (and/or dice), and a lower division, which they will beat a statistically significantly higher proportion of the time than they ought to.
I reckon the lower division consists of the League races (except maybe the Brakiri), the EA, the Drakh, Raiders and Vorlons, the Narn are borderline, top of the second division, the changes to the White Star might have pushed the ISA down into the second division.
Upper division consists of the Shadows (Tourney versions, which I may continue to use or run in parallel with the Armageddon stat) Dilgar, Minbari and Centauri.
Partly this is a gameplay artifact. It's far better to give than to recieve, especially when it comes to heavy weapons fire, and between medium firepower and a high ability to take damage, and high firepower and a mediocre ability to withstand it, I'll take the bigger zap every time.
I do reckon the Sulust is overgunned for it's position in the fleet, but to be honest I'd actually give it more, lighter dice- up it to 6AD and remove the Double Damage. That should make it more viable as an escort destroyer rather than an assassin. It's still capable at it's own level or lower, but can't go big game hunting any more.