Originally Posted by Blizzard Entertainment
We're trying to keep under control the healing abilities of the non-healing classes. Since healer mana is supposed to matter now, self heals become much more potent than they are on live. Warlocks were always intended to sacrifice some health to restore mana, and then restore that health through drains and health gain effects. As WoW aged, that gameplay diminished. On live, you generally Life Tap because of the glyph, and expect overpowered heals to just heal you up. For Cataclysm, we’re boosting Drain Life’s damage and healing and making Life Tap stronger so the lock has more control over his resources.
Affliction is intended to have an edge over the other specs in terms of how much health they gain, through Siphon Life, Death’s Embrace and Haunt. The other specs also have some mechanics to reduce their need to Life Tap / Drain Life such as Mana Feed and Soul Leech.
That said, numbers aren’t final yet. We’re boosting Siphon Life in a future build, but then again we’re also reducing Drain Life’s heal restore. We’re also tuning Life Tap to consume less health, and give more mana for that health consumed.
The new Nether Protection change is designed to give the warlock more control over when Nether Protection procs, instead of it happening in the background with an ICD. If the boss is about to hit you really hard with a Frost spell, you can Nether Ward and count on Nether Protection happening, whereas before it could or could not proc randomly.
Pets: For Affliction, the Succubus and Felhunter will do comparable DPS. The Felhunter will probably come out with a slight DPS edge. But if you were doing an encounter such as Heroic Anub, you would use the Succubus over the Felhunter and you see only a minimal DPS loss. For Demonology, all pets will do similar DPS, but the Felguard will have an edge on fights that require AOE. But you could use an Imp on a Patchwerk-style fight and see a minimal DPS loss vs the Felguard. On the other hand, an encounter like Heroic Freya would make the Felguard shine. For a heroic dungeon, the Succubus helps with crowd control. Keep in mind these are goals, and may not reflect the numbers in the current beta build.