Why don't all weapons imrpove your wc? WC is hard to get, the max is -72. You start at around 17. You gain one per physical level. And one (or two if you spend 2k) for every ring slot you waste. I don't think we are expected to gain anywhere near 20 physical levels just to get to a quarter of the max. That's why i think all weaposn should improve wc.
Bows would improve the msot because it is hard to aim as it is.
Daggers the second most to make up for their obvious shortcomings.
The +6 - +7 swords alot as well to match them closer to the higher damage swords.
Basicaly light or sharp high quality weapons give more wc and cumbersome clumsy weapons give less wc.