I guess I should start out with the caveats. Any too-good-to-be-true offer has fine print, right? Why should this potentially helpful article be different?
In my best legal radio announcer's voice: /deep breath. The views expressed in this article are solely those of the author who, though having played an Affliction Warlock for many years is no longer raiding. His raid group dissolved and he has yet to finish the DS fights, which is probably really sad. Still, he's making the most of it by, well, waiting for the next expansion. The point here is that he may not be on the up-and-up about the newer fights. /deep breath
Sibylle asks specifically about Morchok, which I've actually done a decent amount, so I should be able to help there. Also, I think a lot of what I'll say is generally applicable. Still, I know I have a couple more-shadowy-than-I Warlocks lurking out there that may know things I've missed. (Poneria of the Blood Pact, I'm looking at you. I'll beta-read for you any time, just shoot me an email. You're a rock star in my grimoire. Also, you're blocked at work, hence why you're getting the comment here, in the middle of an article. Convenient, no?) Feel free to help our fellow 'lock out in the comments with some specific tips on DS fights.
If memory serves, on Morchok the basic idea is that you have a small bunch of ranged that are on "shard duty." They have to close with a randomly spawning shard to decrease damage, and do it quickly. Also, there's the whole run-behind-a-rock phase as well. Those are pretty much the two "problem zones," right? (I'm going to assume that most of the folks reading this know what to do if you're just standing there, not chasing anything. If not, check out my guides and feel free to ask questions to that effect.)
Unfortunately, there's not a whole lot you can do running to the shard. It spawns randomly, making it hard to anticipate. Your raid leader can help by positioning folks to minimize the running. That is, we used to just spread out as ranged, and the three nearest did the running. Sometimes, they assign runners though, and if you're one of them and a shard doesn't spawn nearby, it's going to suck.
Even in the worst case, we can do a few things. You have Fel Fire to keep UA up. Corr and BoA/D are instant, so you can keep those up. That alone should keep you from bottoming out. If you get a lucky nightfall proc, that's a bonus. The general idea when running is to keep an eye on all of your instants. Don't let them fall off. Sometimes it goes against the stand-and-sling rotation, I know. For instance, you may want to clip your DoTs (*gasp*), but look at it this way: anything you take care of while running is something you don't have to take care of while standing. It may not be mana-ideal, but you can keep DPS flowing and that's your #1 job.
While running to the shard sucks, running back should be the easy part. I mean, you did drop your demonic portal, right? Right?! If not, it's okay, that's one of my fails, too. After the first run of shame back to your starting point, you'll be like: oh yeah, I should drop that. The portal lets you get back to point A in a green flash, and back to casting right away. Proper portal use is key to minimizing problem zones in a fight. Clever use can almost always boost your deeps.
Bonus, the portal can help you in the hide-behind-a-rock phase, too. He'll yank you in, you port back out. Generally, this lets me find a rock earlier and, in some case, find a space that lets me still DPS the boss. This trick is dependent on lucky rock placement. You have to get it where the safe, non-ink zone allows you to stand and not be LOS'ed from the boss. Porting out, giving yourself more time to look for a spot, only improves your odds.
So, the crux (horcrux?) of performing on the run seems to be possible to distill to two main points:
- Pay attention to your instants. Refresh on the run what you can, freeing up more standing time for cast-time only spells.
- Figure out the best use of your Demonic Portal. This will vary between fights and mechanics, but can usually go a long ways to smoothing out the dead zones in your DPS. It is almost always worth dropping, even if you forget before the fight.
I'll touch on one more trick before I wrap this up. Soul Swap is a great spell to remember to use. A lot of fights combine movement with refocusing on a second target. Sometimes this is adds, sometimes the head, or leg, or whatever. Affliction Warlocks are going to suck on anything short lived (fair warning), but if you just need to bump over sustained DPS (think of the dogs in the Shannox fight), proper use of SS can be a solid bump to the deeps. The inhale lasts for longer than you think, so it's often possible to suck in the dots, let the new thingy spawn, and then exhale on the run (both are instants).
Hopefully this helps. It's not so much a guide as a springboard for specific ideas. The keys can vary widely from fight to fight (especially with portal placement and SS usage), but the basic ideas are the same. Sibylle (and others), if there are other specific fights that are hamstringing you (I think I covered Morchok well enough?), feel encouraged to mention them in comments. Me, or other more shadowy readers will likely have a few tips and tricks. This is a great topic, and a place where I feel like Aff'locks can shine, but definitely requires clever play.