Why build giant explorer vessels...or huge ships you have to turn to shot instead of using the cute little turret idea? The stats aren't the be all end all of the ship, they are just what its combat effects work out to be.
The ship might have looked fine on paper to the Narn before the production run was started, then discovered that the realities of the duties these ships were going to have to face involved more armor and more firepower. Look at our Humvee (how do you spell that?). America went in thinking we needed a light utility car to more some troops around ot control occupied territory, turns out we needed something closer to a light tank and started a retrofit program. The Narns have (or had) a conquest empire, maybe they made the same mistake. They developed a transport cruiser to 'show the flag' and keep the locals in line, but then discovered it was too costly for a sub-standard warship...hence the still produced G'quan, while the G'koth is the fading out of the inventory.
And frankly if it was speed 6 or 7 as most seem to think it should be (and the fluff says it depends on its speed) then its very arguable whether the other raid hulls are better for all missions. Against EA I'd want that laser, similar against a Brakiri skirmish fleet., or abbai...lots of neighbors where a medium laser boat would be the way to go. I do personally favour T'Rann (that the carrier?) as my raid choice and might only switch one out for a G'koth, but be nice to have the option.
Ripple