Infantry Assault Blade and you'll see your other damage go up a nice measure, specifically Plague Strike, Scourge Strike, and Blood Strike.
Hit rating does not techincally increase your chance to hit, it reduces your chance to miss. Your chance to miss is PURELY a factor of the level difference (by way of weapon skill and defense skill, since you cannot buff weapon skill and bosses don't buff their defense skill). At maxed weapon skill you have 400 weapon skill. For bosses their defense skill is equal to their level times 5, just like ours. So, at equal values, 400 weapon skill versus 400 defense, you have 5% chance to hit. The classical values were that this increased by 1% for each of the first two levels the mob was higher than you, and then 3 levels made a bigger jump. Please note: these are hit values for wielding a single weapon and melee hit based special attacks (I'm still testing DK's "spells" for hit rating requirements). So, the % you need to not miss with your special attacks on a mob are not dependent on your wielding a 2-hander or 2 1-hands, and they are:
level 80: 5% level 81: 6% level 82: 7% level 83 (boss): 9%
Heroic bosses are 82. Nothing short of a raid boss is level 83. Hit rating while dual wielding beyond this % goes to reduce your miss chance with melee, which is not wasted, though I wouldn't stress it. To never miss with your dual wielding melee you would need:
level 80: 24% level 81: 25% level 82: 26% level 83 (boss): 28%