In fact, the way we're designed to deal damage in a slow, painful stream, Warlocks downright blow in PvP -- particularly Arenas -- right now. The king of Arenas today is burst damage, and instagibbing an opponent with a zerg is the order of the day. With very few players stacking the necessary Resilience, Arenas are dominated by players who have gear from heroic Naxxramas.
Out of all the cloth classes, Warlocks are the only one without a natural 'out' of a zerg save for the preparation-heavy Demonic Circle (which doesn't break a stun, by the way, and has a meager 40 yard range). Mages still have Ice Block, Blink, and the target-removing Mirror Image. Priests, more than ever, have higher survivability across the board, specially with Pain Suppression, Guardian Spirit, and Dispersion across three trees and a plethora of instant heals. This makes Warlocks Target #1 when it comes to a zerg train in Arenas. And it takes about 4 seconds for us to blow up.
Alright, forget about Arenas. Forget about PvP. What about raids and instances? How's your Warlock DPS stacking up? The fact of the matter is, in this new no-CC mass-pull kill 'em all instance philosophy, Warlock DPS is kind of lackluster. The 2-second cast Seed of Corruption isn't going to be applied fast enough to hit everyone, and there just isn't time or sense to insert Curse of Agony or sneak in a Chaos Bolt or, in my case, Haunt. No, trash is the domain of bursty Retribution Paladins or Mages. I'm happy whenever I get a Rogue in my party because, well, he's a Rogue. And as bad as we've got it right now, I think Rogues have it worse in PvE.
Still, it's no longer the same. Everyone deals a whole ton of damage now, and it's damage of the bursty kind. If it's a long boss fight, then sure, we're right up there. I've been getting better gear and seeing excellent returns some new gear, but it's an aneurysm-inducing chore to keep an eye on DoTimer all the time. I love that I never run out of mana. It's an Affliction thing. Haunt and Siphon Life means I can keep up this thing forever. Too bad fights don't last forever. Or long enough.
This is Wrath of the Lich King, where all content can be beaten in three days, and bosses bend over for you to take their loot. There aren't any extremely long boss fights anymore. Boomkins are no joke and blow DPS meters on trash and bosses. Death Knights aren't funny, either, and Shadow Priests and their ridiculously overpowered Mind Sear give us a run for our money. Here's the thing: in Wrath, any DPS class or spec can now DPS. It's not a free ride to the top of the meters anymore. If we want to perform well, we have to work hard at it.
It's a hit!
First question we should ask ourselves is... do our spells actually land? A lot of the time, DPS of any sort, not just Warlocks', loses a lot from attacks and spells not actually hitting anything. To prevent this from happening, we have to ensure that we're +Hit capped. This question has been asked time and again to Alex Ziebart's frustration in The Queue or TCFKAAABT (The Column Formerly Known As Ask A Beta Tester). I'll cut straight to the chase. It's 446 Hit Rating that will give you a 100% chance not to miss anything in a raid because 26.23 Hit Rating is equal to 1%, and you'll need +17% to touch raid bosses.
You want math? I hate math. So I'll just lay it out simply, if you have 3/3 Supression and 3/3 Cataclysm (which is both in this Affliction build, incidentally), you gain 3% more chance to hit with Affliction and Destruction spells respectively. This brings down the Hit Rating requirement to 368. Still a pretty steep number, isn't it? That's just for raids, though, where bosses are Level 83 (or three levels above you, which is a Skull). In heroic 5-man dungeons, where most mobs will be Level 82, it's a measly 78 Hit Rating with the talents above or 157 without.
If you see a drastic difference in your performance between heroics and, say, 10-man Naxxramas, it could very well be that you're Hit capped for Heroics but not for end-game raiding. If that's the case, then Hit is the first thing we should work on. There's a whole bunch of +Hit gear in the game, many of which drop from Heroic instances.
If you're a tailor or have the money to buy the materials, I highly recommend getting a pair of Ebonweave Gloves and an Ebonweave Robe crafted. These two pieces alone will put you over the Heroics Hit cap if you're talented, and just a Snapper Extreme away if you're not. If you're raiding, the Ebonweave Gloves are a better investment because T7 Plagueheart robes have +Hit while the Plagueheart gloves do not. Tailors can also make the Hat of Wintry Doom, which isn't epic, but has a meta socket and a good amount of +Hit.
Relax, we'll get there
If you're not yet Hit capped, there's no reason to worry. Raids often get the benefit of added raidwide +Hit from talents or, if you're Alliance, a Draenei's Heroic Presence in your party. Shadow Priests have Misery and Boomkins have Improved Faerie Fire (which don't stack). That reduces your need for Hit even more. With an additional +3% Hit coming from either talent, that 446 Hit Rating isn't so daunting now, is it? With either buff and the necessary talents, the Hit Rating needed for raids drops down to 289 (263 for Alliance players with Draenei in the party). If untalented, it's a steep but manageable 368 Hit Rating (342 for Draenei lovers).
Before you go looking to enchant your gear with spell power, consider enchanting your gloves with Precision and boots with Icewalker. All that spell power will go to waste if it doesn't land, so think about getting towards that Hit cap first. Getting it from gear is great and will free up your gems and enchants, but if you don't manage it yet purely from gear stats, we do have alternatives. Instead of a Spell Power flask, go take an Elixir of Accuracy. It's much cheaper and will probably give you better returns until your gear is up to par.
I guess what I want to point out is that Hit is important. Until we get to that cap, whether we're doing heroics or raiding, we're not going to be outshining those Wrath-spamming chickens or hammer-twirling Retadins. It's the first step in the formula to getting back on those DPS charts. Once we've got our Hit down, we can start working on those other stats that make us truly fearsome, namely Haste and Crit (and of course, spell power, silly). Just don't bother stepping into an Arena.