[pharmakos]

basically, there's a damage bonus that gets added to each swing for the main hand only. it is the same number each swing, regardless of the delay of the weapon. if your damage bonus is, say, +10, then a weapon with a delay of 20 is going to have a total damage bonus of 300 each minute, whereas a weapon with a delay of 40 is only going to have a total damage bonus of 150 each minute.

someone else will probably be able to explain it better than me, though.