It's been a long-lamented hardcoded issue that non-Warriors recieve only piddling benefits from increasing weapon proficiencies. When characters who are at least part Warrior (Fighter, Ranger, Paladin, and all their kits, including the Barbarian) add weapon proficiencies, they get improved THAC0, Damage, and Attacks per Round. But when characters who do not have any Warrior levels add proficiencies, all they get is improved THAC0 & Damage. The game engine simply does not grant increased ApR (based on weapon proficiency, at any rate) to non-Warriors.
As for this "gimping" my kits, I don't think that's the case. It certainly cripples the Sharpshooter (from Song & Silence) kit all to hell, though, because despite my repeated explanations to the contrary, Andyr tenaciously clings to the idea that being able to Grandmaster in Bow is enough to make the kit worth playing. But the most powerful feature of all my archer-type kits is not the number of stars they can put in ranged weapons, but rather the level-based THAC0 bonuses with ranged weapons. A Sniper's aim improves over the aim of a normal Thief at the same rate that an Archer's aim improves over that of a plain Ranger. True, the Sniper, Spellshafter, and Huntsman of Silvanus will never be as skilled at archery as the Bowman, Mystic Marksman, and Archer, but that's because they're not Warriors, and nor should they be.
I'm toying with the idea of giving the non-Warrior kits a slight edge to help even them out against the Warrior kits, though: While the non-Warrior archer kits recieve their level-based bonuses to ranged THAC0 and Damage, the Warrior archer kits recieve bonuses to ranged THAC0 only--not Damage. Anybody want to offer some feedback on this idea?