Back when Burning Crusade first came out, a lot of theorycraft shot around the warlock forums regarding the best DPS spec, and the math behind those assertions. The math was done using numbers close to 1k shadow damage, and conclusions were reached, cookie cutter specs were settled into and all was right with the world. Now the warlock forums are overflowing with "OMG WUTS TEH BEST DSP SPECZ" threads, and the answers are starting to get choppy.
Here's the conclusion I have reached, given my own experience, REAL math, and real raiding scenarios.
0/21/40 is the superior DPS spec for a warlock who has reached hit cap. Period. End of story.
Looking through threads on theorycrafting, I usually see numbers close to 2000 damage per second for Destruction, and I see numbers close to 1300 damage per second for Affliction. These numbers are crap, there is utterly no basis for asserting that ANY DPS class is capable of putting out 2000 damage every second for a sustained period of time. To assert this is moronic.
Debunking bad numbers:
My actual experience with destruction shows that over an entire raid, I do about 1100 sustained damage per second. With 1100 shadow damage, 30-33% crit and hit cap, my average shadowbolt hits for around 2600. In order to pull down 2000 Damage/second, your average shadowbolt, a 2.5 second cast, would need to hit for 5,000. Show me a warlock who does this consistently, and I'll show you a warlock who has a private server.
In order for affliction to produce 1400 Damage/second, the 4 DoTs you have to rotate and keep up would have to hit INCREDIBLY hard. Your DoTs and a shadowbolt would need to produce an average 3 second "tick" of 4200 combined. Even with some very generous +damage estimates, your UA would tick for 600, agony would average 480, corruption would be 600 again, and immolate would be around 400. These are very generous estimates when you factor in partial resists and latency, and they require about as much +damage as you can possibly get end-game. What's that you say? I forgot about Shadowbolts?! How dare I do such a thing... An affliction warlock with 1500 shadow damage would see an average shadowbolt hit for around 2000 and given the emphasis on +damage over crit, you wouldn't really see a huge boost with additional crit. (which is why SM/Ruin builds suffer end-game)
An ideal 18 second starting cycle for an affliction lock would look like this:
1 Immolate for 1.5 seconds (2600)
1 UA for 2 seconds (3200)
1 Corruption for 1.5 seconds (3400)
1 Dark Pact for 1.5 seconds (0)
2 shadowbolts for 5 seconds (4000)
1 Immolate for 1.5 seconds (1300 due to only seeing 6 seconds till we hit 18)
2 Shadowbolts (1 crit) for 5 seconds (5000)
1 Nightfall proc for 1.5 seconds (2000)
So, given these generous estimates with immaculate timing, and not counting our initial 1.5 second cast for immolate, we see about 14k damage go out. This scenario is very generous and even includes a nightfall proc, and works out to 775 damage put out per second.
So, now that we have established that real numbers do not get posted on the lock forums, let's talk real-world average cases.
My current gear swap-outs allow two sets of stats while hit capped:
1100 +shadow damage, 30-33% crit and max hit for destro.
1250 +shadowdamage, 18-20% crit and max hit for affliction.
I do 650-700 DPS as affliction and 1100 DPS as destruction. I have *decent* gear for
both specs, and know how to play both, one is clearly better for damage output. (By a wide margin)
So why is affliction still used in BT/Hyjal?
Affliction is still conidered viable in BT/Hyjal for three reasons:
1)Malediction- This talent takes curse of shadows/elements from 10% to 13% and is seen as a huge boon to shadowpriests and mages.
2)Shadow Embrace- This talent reduces all damage done by whatever has a DoT on it by 5% and is considered invaluable for fights with big spike damage, and fairly valuable for all other scenarios.
3)Self-sufficiency- The affliction lock rarely lifetaps, is incredibly mobile and can heal themselves quite well.
The reality is this:
1)In order for Malediction to profit the overall raid, that 3% boost to CoS/Elements would need to total 500 damage per second. given an average scenario of 2 shadowpriests, 3 mages and 2 other warlocks, your other damage classes would need to pump out nearly 17,000 damage per second, or startling 2500 DPS EACH. Malediction also returns 3% more mana/health via the s-priests, but it works out to a negligible amount that can easily be replaced by spellsurge.
2)Reducing all damage a mob does by 5% sounds like a great idea, right? 5% of 8000 is 400, the reality is that your healers still have to heal 95% of whatever that mob does...
Given a raid with 14 DPS players, and an average of 750DPS per person (once again, generous) you end up with a total of 10,500DPS. If you were to bump that number up by 500 DPS you would find that the mobs die 5% faster anyway, and your healers still heal 5% less, have a lower chance of going OOM and your tank dying anyway.
3)Mobility and self-sustaining power are a benefit on a lot of fights, but just not worth the damage decrease of 50-freaking-percent. I could wait 1.5 seconds in between each of my shadowbolts and still put up better numbers than affliction. My priest buddy really doesn't think that tossing me a renew is a burden, and just one allows me to tap to full every time.
In summation, when using real numbers, affliction doesn't compete, and you can argue versatility 'till you're blue in the face. For my money, a mob that dies faster dies better.