IF (and I stress the "IF" there) hunters are "broken" it is only by virtue of the complexity of the class compared to others.
It's stupidly simple to DPS as a Mage by comparison to a hunter - spam arcane blast, do missiles on a proc or something. 90% or more of your damage is arcane blast, 10% or less is missiles.
Hunter rotation is a PITA - you've got to fire steady shots in pairs at least in order to keep the haste buff and you've got to do it every 8 seconds. Chimera every 10 seconds or as close to that as you can get. Arcane when Chimera is on CD and you have focus. Alternate between salvos of Chimera and arcane and double taps of steady. The rotation doesn't really repeat on any interval short enough to consider it repeating. It's all reactive.
You have to monitor at all times the following:
Is Improved Steady Shot buff up (only an 8 second duration and only after two consecutive steady shots land)?
Is Chimera off CD?
Is there enough focus for Arcane Shot?
How many Arcanes can I shoot before a) Imp. Steady Shot Buff falls off, b) focus is drained c) Chimera is off CD (gotta make sure you keep Serpent going).
Is instant Aimed Shot procced?
Is my pet dying to some stupid ability that's an AOE but not considered an AOE by some glitch or intentional joke?
If you manage all of those things properly along with your rapid fire and readiness cooldowns as well as kill shot, you'll do competitive DPS on SINGLE target fights only. If it's a boss fight with an add or two, a DK, Paladin, Rogue, Warrior, with as much as 1500 less gear score will out DPS you because of their innate AOE abilities (howling blast, cleave, divine storm, blade flurry).
AOEing as a hunter is MUCH more involved than other classes for basically substandard results.
You've got to toss an explosive trap and hope the tank doesn't move the mobs out of the splash area, launch a multi and a second if you've got the talent for reduced focus cost on a crit multi, and then go to single target DPS. By then, the single button AOE simplicity of a few other classes has all the mobs nearly dead and you're out of focus and looking for something to put 2 steady shots into so you can get the haste buff and regen some more focus for another multi... usually you wind up trying to shoot something with a steady that dies before the steady lands, so you switch targets and repeat the effort for the next 6 or 7 seconds with no focus gain other than baseline and no haste buff.
If you do it all perfectly you'll be well behind other classes with AOE and you'll have carpal tunnel compared to them.
If the dungeon is full of 4 and 5 mob trash pulls you will see DKs, Paladins, and Warriors with as much as 2k less GS doubling your DPS as a hunter since they're able to do their single target rotations which include inherently (or nearly so) multi-target attacks. A well geared paladin tank will also give you a run for your money on overall damage done in such an instance because of their constant AOE damage and the fact that you are constantly trying to single target DPS when everyone else is AOEing because your AOE is not efficient for fewer than like 6 mobs while their single target DPS is twice as efficient on 4 mobs as it is on one.
So, does that make hunters broken? Or does that make other classes broken?
Hunters need volley back for AOE, that's a given, and it needs to be cheap in focus cost. Hunters need some focus changes. The haste buff from Imp. Steady needs to last longer or just be removed and be a part of the spec. Steady needs to return more focus.
Oh yeah, and on fights that don't last long, hunter DPS suffers considerably compared to other classes due to lack of burst, long cooldowns, travel time and interface lag on kill shot.
With all of that said. I am enjoying my hunter now more than I have in a long time. It takes some thought and if you do it right, you get good results. I expect other classes to be tuned to be more demanding and less overpowered going forward. Hunters are now to DPS classes what Warriors have always been to tank classes.
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If ignorance were painful, half the posters here would be on morphine drips.
Everyone playing WoW knows everything about playing two classes: 1) their own and 2) Hunters