The formula is as follows:
Some weapons use just STR (maces, clubs, etc) and some use the average of str and dex (swords, etc).
A random number is generate between the max damage a weapon can do and the negative of it... say if it does 15 damage: its random between -15 and +15.
Then your str comes in. based on your str, a bonus is added to this random number (not just your str, but a derivative of it) say your bunus is 7, then the number would now be -15+8 to +15+8 which is -7 to 23.
If it is over the max damage of the weapon, then it is capped at the max damage(which is why you do exactly 15 more than you do 14), and if it is less than 0, it is counted as a miss.
Any armour they have is then subtracted linearly (i.e. if you got a 10, and they have 4 armour, you only do 6 damage), multiple weapons are done separately... so against unarmoured things, a 2handed weapon doing 30 is the same as 2 one handed weapons doing 15(i think)... BUT.. if they have armour, a 2 handed weapon only looses it once, not once per weapon.
Dex bonuses such as swing rate and dodge bonus are balanced by the str bonus of allowing you to both carry more, and to equip more. You gotta be pretty strong to have both armour AND a halberd.
Thats why i was so for the halberd being good, since its really hard to lift it. I do think there should be some other str bonuses now that hirelings and houses take away the bonus of carry ammount. The swing rate and walk speed is very small, but dodge percent is pretty good.