Hunter 3:2 rotation and spell queuing mechanics

[Zarant]

Once the 0.5s Auto Shot cast time starts, it shouldn't be interrupted by other spell casts, all spell casts performed during the Auto Shot wind up time should be queued and handled by the server immediately after the auto shot goes off.
Source: https://web.archive.org/web/20080211131225/http://elitistjerks.com:80/f31/t11420-hunter_beast_mastery_bible/p109/ - see the last post, from January 28th, 2008 (patch 2.3.3)

That particular mechanic gave birth to the 3:2 rotation because it had a small quirk to it. Once a steady shot was fired at the start of the auto shot wind up time it would trigger the client side GCD and queue the steady shot, which would start casting 0.5s later not triggering the GCD a second time, giving the hunter a 0.5s heads up.

One could argue that the 3:2 rotation was caused by a bug completely unrelated to the spell queuing mechanics added in patch 2.3, but as a consequence of the GCD handling, and the source above illustrate that, however, that might as well be an intentional mechanic, since the 3:2 rotation addresses ranged weapon scaling for BM Hunters.

Straight from the EJ post above, you can see the rotation breakdown using a 2.9 speed weapon with 15% haste quiver and an extra 20% haste from the standard BM spec, resulting in a 2.9s/(1.151.2) = 2.1s attack speed and a steady shot cast time of 1.5s/(1.151.2) = 1.1s

-.5s GCD starts, auto starts
0s auto
1.0s GCD finishes - GCD finishes before the steady shot cast time allowing the 2nd shot to be cast right away
1.1s steady
2.2s steady
2.6s GCD finishes, GCD starts for next steady
2.7s auto - By casting 2 steadies during the previous cycle the auto shot timer is slightly delayed
3.8s steady
4.1s GCD finishes
Either:
5.2 steady
or
4.8 auto (with the auto cast starting at 4.3s and starting the GCD for the next steady)

In this case, the 3:2 cycle, consists of 5 shots and lasts 4.8s (1.04 shots per second), a 1:1 yields 2 shots every 2.1s (0.95 shots/s).
If the GCD started at the beginning of the first steady shot cast, a 3:2 rotation would yield 5 shots every 5.2s (0.96 shots/s), which is just a marginal upgrade over the much more mana efficient 1:1.

Although it may at a first glance look like a bug, after reading hundreds of pages of that EJ post, I realized that it might as well be an intended mechanic in order to address the issue of hunter scaling, the 1:1 rotation scales a lot better with fast attack speed weapons, which makes weapons like Wolfslayer Sniper Rifle and Don Santos Hunting Rifle better ranged weapons than any of the T5 or T6 ranged weapons.
Here is a quote from Cheeky, the person responsible by creating one of the most complete hunter spreadsheets from the TBC era:

For most purposes damage from RAP, ammo and scope completely swamp the advantage of a weapon's higher inherent DPS. And faster weapons allow you to remove dead time from your shot rotation and get more Steady Shots out. Except for extreme cases (bows faster than 2.4, 20+ DPS difference) a faster bow is always going to put out more total damage in a BM's Auto/Steady rotation. But your mana efficiency goes down as well, since more Steady Shots means more mana, and lower DPS weapons have lower damaging Steadies.

Source: https://web.archive.org/web/20080511005528/http://elitistjerks.com:80/f31/t11420-hunter_beast_mastery_bible/p45/ - June 19th, 2007 (patch 2.1.2)

According to Cheeky's spreadsheet (https://web.archive.org/web/20081004051530/http://elitistjerks.com:80/f31/t9816-hunter_spreadsheets_--_development/), using a 1:1 rotation, Wolfslayer Sniper Rifle is the best in slot BM hunter weapon all the way to sunwell. Which kinda explains why blizzard never fixed the alleged GCD bug after a major patch (2.4) and at least 3 minor patches. Since the 3:2 rotation slightly clips an auto shot, it scales way better with slower attack speed weapons, which makes all ranged weapons from T5/T6 content viable once again for BM hunters.

[Summoning01]

There was another bug (something with the '!Auto Shot' in macros) that let players fire an additional special shot, but it got hotfixed after a day or two iirc. Some people are confusing that bug with the queue mechanic.
ps. you forgot to link this http://wow.allakhazam.com/wiki/shot_rotation_(WoW)