I have personally seen a high level multiclass rogue do over a hundred points of damage in half a round with some lucky crits, and that was against a fuly buffed character of decent level due to a missclick with knockdown during a Perfidus run. Given ideal setup, there are a lot of combinations that can achieve similar things, for example the infamous scythe using Weapon Master, who can crit for over 200 damage, effectively killing most characters in a single hit. There are a lot of factors at play here, but in NWN and especially in PotM where there aren't many high end magic items to make up for a lack of buffs, characters that are buffed and prepared will always seem overwhelming when put up against those that are not. I think it is not good practice to use a single incident in a vacuum to make such claims.
As for it being PvP, ranged attacks also have the disadvantage of being obsolete as soon as your target steps behind a cover, and they also don't get attacks of opportunity whenever your target drinks a potion, casts a spell or uses a scroll. And of course you can always argue that you can ambush someone in the open field, where there is little cover and hard to get away, but that takes us back to the previous point of perfect setup. You can easily argue as well that a melee class with just basic buffs or even no buffs getting the drop on someone with no points in Discipline would be just as deadly, if not more. And in the same sense of perfect setup, as you put it in your post, you could do the opposite and catch him in melee, which makes him much less potent. There is counterplay already present in that system and it is up to the individual players to acquire the favourable setup for themselves. I still disagree that Bane Bow is as strong as you make it out to be.
But I digress, this is not a psot about balance but about suggestions for the hak update. As for actual suggestions, I would love to see some of the Large Shield models be used as Tower Shield models, especially the round Viking shields, as they are fairly big, bigger than even a fair number of Tower Shield models, and there are only two round Tower Shield models available currently.