Not excitingly, most of Patch 3.0.8 consists of bug fixes, so there won't be any major changes to gameplay or dramatic shifts in the way we do things. The biggest change is arguably in the way Ritual of Summoning works, which will save us Soul Shards the way Soulwells changed how we handed out candy. The new mechanic creates a sort of summoning object -- currently some sort of infernal flasher who opens up his cloak -- that works almost exactly like an instance summoning stone. This is great for raids, but not so hot for parties when you just want to summon one person. It has a cooldown of two minutes (down from the originally planned five).
The other really big thing is the new tagging -- or tapping, as Blizzard likes to call it -- mechanics. In Patch 3.0.8, "all player spells which cause a creature to become aggressive to you will now also immediately cause the creature to be tapped." This means no more annoying Hunters stealing our mobs with a stupid Arcane Shot before our Corruption has had a chance to tick. No class benefits from this change more than Warlocks, so while it has practically no application in raids and dungeons, it's been a long time coming for the common grind.
The good news is that the simple bug fixes actually improve our DPS somewhat. It's not huge, but after mind-numbing tests on the PTR, I'm breaking out about 200-300 more DPS on the same spec with the same gear than on live for Affliction. I gave 0 /41 /30 a shot, too, but I wasn't properly Glyphed for it and wasn't comfortable with Conflagrate Incinerate spam. On the other hand, other Warlocks testing -- and swore by -- the same build were getting better results on the PTR, as well. Overall, the Patch looks decent for the class and we'll be seeing more buffs than nerfs in general.
Yes, there'll be nerfs, as well, although not to Demonology as originally indicated by the Patch notes. Debuffs in general will be affected, thanks to the change in dispel mechanics, which removes Fear (among other crowd control spells such as Seduction) from the umbrella of dispel protection. The change effectively nerfs debuff classes such as Death Knights and Warlocks but buffs dispelling classes such as Paladins. The change also mostly applies to PvP -- where Warlocks already suffer -- but we're getting some buffs in that department, too.
The most important one is that Demonic Circle should now remove all snare effects, which should improve our survivability quite a bit. Not sure if this means stuns, too, although the wording doesn't seem to indicate that. For all intents and purposes, though, it should ideally work similar to Mages' Blink as a means of escape. Also important on the PvP front is how Demon Armor and Demon Skin have had their armor increased by about 120%, with the former granting 2100 bonus Armor, up from 950 on live. Just how much these changes will improve our survivability in Arenas or PvP in general remains to be seen, but it's definitely an improvement. As a side note, the Demonic Circle trick will no longer work in Dalaran Sewer Arena (which for many of us was the only thing that let us last the match for longer than 20 seconds).
Drain Mana was reworked to drain a percentage of maximum mana instead of a set amount, so there's now only one rank of the spell (it'll disappear from your bars, took me a while to find this on my Spellbook). This change helps low-mana specs like Retribution and Enhancement, but also means we can actually put a dent in a Mage's kajillion-mana pool. That should be sweet. It also now generates a small amount of threat, which means Blizzard should probably get on improving Soul Shatter.
Glyph of Conflagrate has changed to no longer consume Immolate or Shadowflame, making it work more like Glyph of Flame Shock. Curse of Agony will scale better with Glyph of Curse of Agony, with each subsequent tick beyond the original duration dealing 33% more damage than the previous one. This should provide a decent DPS increase and should remind us all not to clip our DoTs.
Finally, the other big change is the fix to demon scaling. Summoned demons will now have higher health and deal more damage, and scales properly with Fel Armor, amounting to about a non-scientifically tested 30% more on my Felhunter on a dummy. It's actually smaller than it sounds, considering that it contributes only about 150 DPS on live. That's not much, but it should scale better in a raid environment.
Overall, Patch 3.0.8 is going to be a good one for us. But the real good news is that Blizzard is working hard on making bigger, more impactful changes for the next major patch, Patch 3.1. Ghostcrawler has already called on the Warlock community to contribute, asking which spells don't deserve a slot on our bars. They have their own plans for the class, but want to "make informed decisions", which is a good sign. I know the changes can't come soon enough, but true fixes will take time.
Changes we can look forward to is a major revision to the Soul Shard mechanic, one which Ghostcrawler promises to be "very cool." I hope that cool in his definition includes easing up the requirements for spells like Shadowburn, Soul Fire, and Soulshatter. If those spells didn't empty our Abyssal Bags like Homer Simpson wipes out a box of donuts, I guarantee that they'd find their way to more rotations.
Affliction is way fun, although many of the Warlocks I've spoken to on the PTR are swearing off the spec because it makes their eyes bleed. Blizzard's looking at that, too, with options on making durations more uniform or reducing the number of spells to cast. My take, personally, is that Haunt should refresh more DoTs than just Corruption, which should ease up the Affliction priority cast cycle considerably. There's probably the danger of making Haunt a little overpowered, but I know that casting it now takes highest priority because it saves me one GCD and because of Shadow Embrace. It's mandatory enough as it is when going deep Affliction, so making it a lynchpin spell just makes sense to me.
The last great thing I'm excited about is a promised change to demons. While we shouldn't expect demon DPS to rival those of Hunter pets, Demonology is one spec that should receive massive returns from demons. Considering deep Demonology is sub-standard for raiding -- 0 /41 /30 being the best Demonology spec right now -- Blizzard is looking at improving the Voidwalker, Succubus, and even the new and improved Infernal and Doomguard. A true utility spec with competitive DPS would be a welcome change, indeed. All told, Patch 3.0.8 is merely something we'll need to get by until we get to good stuff.