Hello,
About weapon skill affecting hit, it's a formula, based on what http://vanilla-wow.wikia.com/wiki/Hit says. Basically until +4 skill it gives .4 hit, and the last +1 skill gives 1.6, so trolls and dwarves get 3 hit ( basically a free hit scope, so they can put 7 damage on their weapon).
Now, about the damage numbers, it's been done here: http://forums.elitistjerks.com/topic/82 ... breakdown/ (you should login with facebook). It basically states what the best weapons are:
1. Kel'Thuzad xbow (599 dps)
2. Chromaggus xbow(571 dps)
3. Ouro Gun(558 dps).
So basically the +skill races wouldn't get much love in the end game, but I'd use the ouro gun as a dwarf against the xbow, just to be true to the race xD.