That's not a problem in TC, where hull values aren't drastically increased. Since the Agamemnon and Diemos have impressive amounts of shielding for their class, they can easily afford to ram other ships in the same class (or lower) after taking the shields down even half-way. Even 4 PSGs are more than capable of dropping the shields during the approach for a ramming attack (just hold down the fire button and charge), and the enemy ship simply evaporates on impact, while you've still got plenty of shield strength left. The Paranid capital ships aren't optimal for use against some of the other race fleets, but are the perfect tool for the task in OFF.
Ridiculous numbers of Kha'ak "Scout" fighters are no problem, because the area effects of a PSG are more than sufficient to vaporize entire waves of them. Other turret weapons simply can't compare in this role. As said, using them in race sectors is a problem, because of collateral damage to EVERYTHING within their general arc of fire and range. Just don't send two Paranid capital ships in together and keep them close, or else you'll end up with only one capital ship in short order, badly damaged. The good part is that they have no need of escort; the bad part is that any escort you do give them will not live long, even if the enemy never fires a shot at them.