The problem here, is understanding the underlying way WOW calculates DPS. From what I remember, there was a range for a certain weapon yes, as well as an attack speed, and then some formula for calculation the damage per second of that particular weapon. You would need to know that formula (or the mechanics of it) to continue with what you are doing because a weapons damage per second is based on how long it takes to make one swing correct? Increasing the attack speed, decreases the speed of the weapon, increasing the damage per second (since base damage is constant).
Another problem is that you really aren't finding a formula for damage per second, but the long run AVERAGE of damage per second. For example, [url=http://www.wowhead.com/?item=47001]this weapon[url] has a range of values from 227 to 453 for some value X. I would say this is a continuous random variable (there some algorithm being done in the background that rounds up or down the calculated damage), and you need to know the probability of such a value before you can start doing any calculations on it. Say for example WOW calculates the damage for ANY weapon and the probability of getting a value between a and b is:
Therefore we'd want the average value of this function (the integral) over the possible values of X:
Without knowing much more about how WOW operates behind the scenes, you're kind of limited in how much TRUE calculating you can do. At best, you can simply log your hits over like I dunno 100 (just to be safe), and see what values of those you produce, construct a histogram, and then see if a pattern emerges in the shape of such a histogram.