Theoretically, WC1 capships had plenty of firepower, but that simply wasn't simulated ingame. They are "there", we just don't see them being used. WC2 had some stuff lige the AMGs and the cutscene-only(IIRC) PTC.
WC3 had cartloads of turrets, and 3 kinds of them! laser, white (i think the whites were tachyons) and yellow (i think these were AMGs). The Corvette was a tough customer, for it had a tachyon turret on the top-aft, and a good cover of 4 lasers, and it was too small to waste a torpedo, so we had to strafe the turrets and all. Also, it didn't have the glaring blindspots the bigger ones had...
WCP had the most variety... HARM loadouts, lotsa turrets you HAD to kill if you wanted your torpedoes to hit (especially those damn transports) and ship components...
But we never got to see some wicked capship-capship combat.
BTW, the WC2 Kamekh *didn't* have phase shielding...