I just ran a short series of tests - and something does seem to be off.
Level 28, 12 monk, 6 rng, 2 pally, halfling. 2% doubleshot (I didnt care to wait 4+ hours for ship buffs to fade which I ideally should have). 22% haste from Blinding Speed. Using a ML 22 TF Longbow (to avoid procs etc).
Each parse is roughly 3 min long. Target is the Magefire Cannon in Proving Grounds on the ship.
Parse counts number of "pierce/slash damage" + number of "miss" -1 as total number of hits as well as end_time - start_time. (minus 1 because I both have a hit at the start and the end of the parse).
Each situation has been parsed twice.
Auto attack: 1.18 attacks/sec and 1.18 attacks/sec
Mouse down: 1.18 attacks/sec and 1.20 attacks/sec
Spamming attack key: 1.29 attacks/sec and 1.27 attacks/sec
Obviously, the 2% doubleshot is a possible source of error but the results seen above certainly seem to indicate that spamming the attack key may result in more shots fired than autoattack/mouse down. The actual number of attacks isnt interesting - but the difference certainly is.
It would be very usefull if someone else would care to repeat these kinds of tests to see if they can verify the results I am getting.
Raw data here (not very userfriendly):
https://www.dropbox.com/s/pl1f9f4mw3...data.xlsx?dl=0