You definitely miss a lot when you take fast shot, especially as burster... don't ever pick that as a burster, for your own sake.
We've discussed it with Chota. While on paper it looks exactly like you've written, think of a situation where you both have similar weapons which have for an example 60 AP cost. Now here is the deal: You have doubled your CHANCE to miss, BUT you've gained a CERTANITY to shoot the 2nd shot FIRST, which may be a decisive one, because of crit and even if not, you will still be able to shoot 3rd and so on earlier.
That's the deal, not "dps", this is no regular WoW.