Quoted from: http://us.battle.net/wow/en/forum/topic/5150757347
Honestly, what a damn joke. Honestly, the OP's concerns weren't even addressed, specificallyWe think the mana costs for Demonology feel pretty good and of course Destruction's mana works totally differently now. For Affliction, we agree that the mana costs are too high - possibly way too high. As some of the posters above pointed out, there is also a bug with some channeled spells, most notably Malefic Grasp, that charge an extra tick at the end. That isn't helping any.
We think Life Tap as a way of restoring mana works and has been a warlock staple for a long time. We just think Affliction locks on beta right now are spending too much of their time having to do it.
1) Life Tap no longer scales with gear in terms of mana return, but scales in terms of cost (with health increase). It needs to scale, in terms of return, with Intellect/Spell Power or even scale with health (such as the current version: a % of the health siphoned is returned as mana).
2) With the loss of Mana Feed (which, in my humble opinion, should be returned) we will be life-tapping more than ever. I'm not against this (since it reduces pet micromanagement/dependency) but we would need to have costs adjusted to make sure we don't do it too much, and don't spend literally all of our health doing it.
3) In Beta, right now I'm burning literally all of my health tapping on a dummy as demonology - something isn't right. The way I see it, for the most part DPS should not need to worry too much about mana compared to healers (where regeneration stats, i.e. Spirit, become required) and we should for the most part be self-sustaining with mana without too much effort spent on regeneration. Because let's face it, wanding while waiting on mana is just a shitty game.