Firstly, for all readers, the

Firstly, for all readers, the following is not a “rant” nor is it the summation of complaint from a warlock displeased with warlock threat management rather it is a reasonable, logical look into the heated debate over the issue. So, in other words, “no QQ please!”
It’s a common scene, the boss running directly to the warlock and stomping his face in, but who is at fault? The Warrior for not being able to generate the godly amount of threat that would have been needed to keep the bosses attention? The healers for not being able to keep the giant boss from one-shotting the cloth wearing warlock? Or the warlock for causing too much threat? Most people would of course blame the warlock and claim that he needs to make use of his threat dump and watch the threat bars. The Warlock certainly then claims that his “threat dump” is worthless, or on cooldown, and his death was not his fault and, of course, the raid calls bull. But who is right? Is the Warlock’s threat beyond his management or is the raid right and does the warlock need to “watch his aggro”?
So the answer can be understood by all, time to break it all down and look at the facts. Let us first look at the Warlock’s side of things, he claims that his threat reducing ability, Soulshatter, is useless. Start by looking at the ability itself, it has a scaled health cost of 8% of the warlock’s base health which, while not a lot, is more than a small amount of health. The Spell also has a cooldown period of 3 minutes (which was reduced from 5 minutes by the latest patch, however this change was seen by some as “a band-aid on my arm for the broken leg” but I digress) and also requires the warlock to have a the max 100% hit rating to not have a chance of failing. Additionally the spell has the reagent cost of a soul shard, so of course any logical person would agree that the cost of the spell, combined with the cooldown (considering the average length of raid encounters), would seem rather costly. Considering this, could a person also agree that a 50% aggro reduction with 50 yards seems rather abysmal when compared with pure threat reducing spells used by other “pure dps” classes? I would think so. For the purpose of supporting this, here is a little chart comparing a warlock’s Soulshatter with similar abilities, specifically a hunter’s feign death, a mage’s invisibility, and as an offshoot a mage’s ice block because of the effect of the spell.
Cost Cooldown Time needed for effect Effect/Threat Reduced Soulshatter Soul Shard and 8% base health 3 minutes Instant 50% threat reduction in 50 yards Feign Death 3% base mana 30 seconds Instant
Lasts up to 6 minutes 100% threat reduction with all enemies in area Invisibility 16% of base mana 3 minutes 5 seconds
lasts 20 seconds 100% threat reduction, invisibility (duh) Ice Block none 5 minutes Instant
lasts 10 seconds Unable to move or act but immune to all spells or physical abilities
So, looking at the chart, first start with the cost column, Soulshatter requires 8% of a warlock’s base health and a soul shard, Feign Death requires 3% of a hunter’s base mana, Invisibility requires 16% of the mage’s base mana, and Ice Block costs nothing at all. Therefore in order from most cost effective to least cost effective the order is Ice Block, Feign Death, Invisibility, and then Soulshatter (note: the last two can be arguable, 16% of your base mana versus 8% of your base health plus a soul shard is difficult to determine). Second is the Cooldown column, Soulshatter has a cooldown of 3 minutes, Feign Death has a 30 second cooldown, Invisibility has the same cooldown of Soulshatter at 3 minutes, and Ice Block has the longest cooldown at 5 minutes, therefore the order of shortest to longest is Feign Death, Soulshatter AND Invisibility, then Ice Block. Looking at the next column (“Time needed for effect” might cause some confusion at first, but to clarify it was called this because of invisibility) you will see Soulshatter has an instant cast time with no duration or time needed to take full effect, Feign Death also has an instant cast but, in contrast to Soulshatter, can last up to 6 minutes (allowing a hunter to cause 0% threat for up to 6 minutes). The last two are Invisibility and Ice Block, the later has an instant cast and lasts 10 seconds while the first, Invisibility, has an instant cast, but takes 5 seconds to take full effect and lasts 20 seconds.
Now to take a look at the most important, and the last, column named “Effect/Threat Reduced”. First up is Soulshatter, it reduces threat by 50% for all enemies within 50 yards (note: requires 100% hit chance to not fail). Second is Feign Death, It reduces threat by 100% for all enemies within the area (within the same zone) and lasts up to 6 minutes (note: has 6% chance of failure, or 17% if the target is 2, or 3 levels above the hunter). The third is invisibility which over five seconds reduces threat by 100% and also gives the mage invisibility and removes them from combat for 20 seconds (unless hit by effects that remove stealth ex: area of effect spells). Lastly is Ice Block which, while not reducing threat will make the mage invulnerable for 10 seconds, giving a tank time to regain threat from the mage. For the purpose of comparing all the spells together, you must look at each of these columns individually and then as a whole, doing so you will find the following
Cost
1. Ice Block
2. Feign Death
3. Invisibility and Soulshatter
Cooldown
1. Feign Death
2. Invisibility and Soulshatter
3. Ice Block

Time
1. Feign Death
2. Ice Block
3. Soul Shatter
4. Invisibility
Effect
1. Feign Death
2. Invisibility
3. Ice Block (technically interchangeable with 2)
4. Soulshatter
Overall
1. Feign Death
2. Ice Block
3. Invisibility
4. Soulshatter
By studying/comparing these abilities this closely you realize that a hunter has the most effective threat reduction ability of the three classes compared, the mage is a close second as a mage holds two abilities that can be used for the purpose of threat reduction, and the Warlock comes in at third with Soulshatter. Now you must consider the average amount of threat generated by these classes during raid encounters and then compare them with these results. First, one must note that the more damage one does, the more threat they will cause, and using the current in game formula 100 damage equals 10000 threat. However, one must consider that some classes have threat reduction talents. The Warlock has Destructive Reach in the Destruction tree reducing threat caused by destruction spells by 10% and Improved Drain Soul in the Affliction tree reducing the threat caused by affliction spells by 10% also. This means with the talents for a warlocks spec, he will cause 9000 threat per 100 damage (100*100=10000-(10000*.10)=9000). Next a mage has Arcane Subtlety in the Arcane Tree which will reduce threat caused by arcane spells by up to 40%, Burning Soul in the Fire Tree which will reduce threat caused by fire spells by 10% and Frost Channeling in the Frost Tree which lowers frost spell threat by 10%. This means a mage will, with the relevant talents, will cause 9000 threat per 100 damage (100*100=10000-(10000*.10)=9000) or will cause 6000 threat per 100 damage (100*100=10000-(10000*.40)=6000) if the mage has Arcane Subtlety. While a Hunter does not have threat reduction talents he has the most effective threat reduction ability (Feign Death) and has the ability to “transfer” threat to a tank by using Misdirection, Misdirection will make the next 3 attacks of the hunter increase the threat of the target rather than the hunter (i.e. “transferring threat”). Considering Talents and abilities together, the order of threat caused is generally..

Threat Caused
1. Warlock
2. Mage
3. Hunter
The reason for this is because of the combination of not only talents and abilities, but also among the higher ends of 10 and 25 raiding the amount of threat generated by a warlock goes beyond that of the mage slightly because of talents and far above of hunters because of the short cooldown on Feign Death which allows a Hunter to better manage his threat without the need for talents. The consensus among high end players is that Warlocks are always riding a “razor edge” on threat meters falling just short of tanks and sometimes surpass them which then leads to death in many cases and although there is no real way to give hard proof of this by maintaining threat charts similar to posted damage/dps charts, there is such a large agreement among the high end raiders that such is the case that attempting to prove otherwise is difficult. Therefore, all things considered everything lines up in the follow way..
Hopefully you see the problem. The class which causes the most threat is also the class that is least effective at reducing/maintaining their threat caused. Before anyone says “well, duh, if a class is less effective at reducing/maintaining threat, then it will cause more threat!” please stop and consider that using abilities like Feign Death reduce/eliminate threat that has “already been caused” while talents only reduce threat that “will be” caused. You picking up what I’m putting down so to speak? If you are not, take a break, or read the above charts and information again and if you do understand; excellent. To clarify better, If you don’t use specific names for classes, but rather class A, B and C you can look at a good example. If Class A is causing more threat than Class B and Class C, even after talents, then it would make since to have the most effective threat reducing ability would it not? Class A would have the most effective threat reduction talent, Class B, second in threat caused after talents would have the second most effective threat reducing ability, and Class C, causing the least threat after talents, would have the least effective threat reducing ability. Makes sense doesn’t It? Therefore, Considering that the order of abilities that wipe threat from most to least effective should be directly converse to the order of threat caused, meaning things should line up like this..

However, against logic and in the face of reasoning, things don’t line up this way, maybe someday things will change, and maybe they won’t. In the end change can only be hoped for because it is up to Blizzard how things will change, if they change at all. Thank you for reading.