So, to start off with, we use this basic (trust me it's basic) formula for DPS:

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All the values over 100 or 10000 are considered their original (non-percent) values, so if you have 25% IAS, you plug in 25, not .25 (the equation makes it .25 BUT THIS IS BEYOND THE POINT OK?). Now the cool thing we can do with this equation right here, is figure out which block is the lowest currently, which makes increasing that block by a significant amount (let's say the whole block +1) will have the greatest impact.
Let's plug in some hypothetical stats (minus sharpshooter, fuck sharpshooter).
1400 Dex
1100 DPS Crossbow (1.1 BAS)
-Average damage (total) 1000
-As a note, this damage already includes +Damage% and elemental damage, and is shown on weapon tooltips. However, I took IAS out of the tooltip values because IAS is weighted depending on the weapon. (25% of 1.6 is much better than 25% of 1.1)
20% critical
200% (bonus) critical damage (Character details here would show 300% critical damage)
50% attack speed
(1.1(1.5))(14)(1000)(1+(.2)(2)) =
32340 DPS (And also because fuck you sharpshooter, DPS with that stacked would be 92400)
Now, let's see, at this point, how much everything is weighted to improve upon this DPS. I'm going to ignore sharpshooter for this because fuck it and trying to weight anything while considering 100% crit means crit damage wins. Always. That makes for boring math. The way to figure this out is to take some value, and increase it by X, then figure out what you have to change the other values to to get them to the same value. Our baseline will be 10% attack speed increase (pretty small). New DPS is
34496. Plug this in as DPS, revert the IAS, keep all but 1 field static, solve for X.
10% IAS = 93.33 Dex = 66.66 Average Damage = 4.66% crit chance = 46.66% crit damageSo increasing any 1 stat by the above amount would result in the same DPS increase. In this example the Attack Speed was pretty low to start, so lets look at a build where IAS is more centric, a 1h crossbow build.
1400 Dex
900 DPS 1H Crossbow (1.6 BAS)
-Average damage (total) 562.5
-As a note, this damage already includes +Damage% and elemental damage, and is shown on weapon tooltips. However, I took IAS out of the tooltip values because IAS is weighted depending on the weapon. (25% of 1.6 is much better than 25% of 1.1)
30% critical
100% (bonus) critical damage (Character details here would show 200% critical damage)
100% attack speed
(1.6(2))(14)(562.5)(1+(.3)(1)) =
32760 DPS (Only 50400 DPS with Sharpshooter, the low crit damage really hurts the "OMG HIGH" dps numbers, as well as having a base higher crit chance)
Alright, same plan as before, upgrade IAS by 10%, see where the rest need to be to get the same effect! New DPS =
34398. Already we see that increasing IAS does less for this build, because its IAS was already so stacked.
10% IAS = 70 Dex = 28.125 Average Damage = 6.5% crit chance = 21.66% crit damage
As you can see, since the IAS and crit chance were higher to begin with, it is much easier to equate to 10% IAS for the other stats. For comparison:
Build 1: 10% IAS = 93.33 Dex = 66.66 Average Damage = 4.66% crit chance = 46.66% crit damage
Build 2: 10% IAS = 70 Dex = 28.125 Average Damage = 6.5% crit chance = 21.66% crit damageIn build 1, IAS is clearly highly weighted, while in build 2, crit damage and weapon damage are very strong. Hopefully this equation makes it easier to figure out where you can get the highest damage increases before buying stuff off the auction house. To use for yourself, follow these easy steps:
Step 1: Plug in your numbers to the DPS equation, simplify it down like I did to (IAS block)(Dex block)(Damage block)(Crit block)
Step 2: Increase one of the values by a hypothetical amount, generally lower is better so things are more plausible, solve for new DPS
Step 3: Change one of the other values to X, change all other values to base amounts, solve for X to reach new DPS
Step3a: Repeat step 3 until you have equivalent values for each stat you can get.
Step X: Consider all the other random crap you can do, such as get on-hit effects. Generally each effect will have a stat that it works with the best.
-On-hit: IAS
-Sharpshooter: Crit damage
There you go, easy math for easy DPS calculations to figure out where you want to improve your stats to get the highest DPS returns. I recommend -never- considering Sharpshooter DPS as it will only cause you to place 0 weight on crit, and 1000x weight on crit damage.
Want to skip even more work? Use the spreadsheet online!
https://docs.google.com/spreadsheet/ccc?key=0AuBq96zIjVoldG1BYm5hVzBfZ0RnajVpWkRyN092dFE