as a rule, the weak weapons aren't a huge problem, thay are twin linked anyway, and against a hull 6 ship, 6 6 remains a 6. They have a reasonable number of dice. and Quite a few people have mentioned the omega, but the G'Quan has 2 sets of secondary weapons, the Omega does not (unless you count it's anti fighter guns). Close in, few ships can match the sheer volume of Dice that can be thrown by a G'Quan, even most war level ships don't have that many dice, and at the end of the day, this is adice game, where rolling often means more than AP, or double damage. More dice should promote more crit potential.
No matter what the damage tracks, the BinTak is one of the best warships out their, and who can deny that a pack of Ka'Tocs can punch above it's weight quite well. I have effectively beaten Vorlons and Centauri in a campaign (not so in the tourney, stupid fan heads), yet been less effective than another primative race, the Dilgar... I won but it hurt like crap.
Just because Narn guns don't have AP all round like the Brakiri, or the range of the Minbari, doesn't mean a thing, it's just numbers, the Ion torps, Mag gun, e-mines are all advanced weapon systems. You have to remember, the Narn developed from a farming slave race, to a major space power, cutting out all the bits inbetween. the later development of the KaBinTak and G'Vrahn shows what the narn are capeable of, when they begin to understand the technology rather than just retrofitting centauri equipment.