DPS Without Sharpshooter
Attack Speed (from details tab. It will be something like 1.1 or 1.5)
Crit Chance % (Without Sharpshooter.)
Crit Damage Bonus %


DPS That Blizzard Show you:
DPS you can actually expect:

So Sharpshooter ends up showing you a very large dps because Blizzard uses a very simple formula to calculate dps based on your crit chance. They assume your crit chance is static and fixed. However, Sharpshooter gives you a varying crit chance. So when you have time to look at your dps, most likely your crit chance has gone up to 100%. So Blizzard is showing you your dps, as if you had a 100% crit chance. What's most likely to happen is, you fire your first shot, and it's a crit. Then your crit chance is going to go down to your base, and increase every second until you crit again. So the actual dps you can expect to hit is much lower. What I've done here is calculated an expected dps based on these values. The actual calculations are visible pretty easily since it's all done in Javascript. So you can just view source.

Fixed a couple of bugs. The previous version was written assuming that attacks per second would never go greater than 1 (since I didn't realise that's possible). It also had an interesting bug in that it assumed that if you crit in a particular second ALL the attacks would be crits, which is wrong. So it was over-estimating sharpshooter dps.