With this lifetap nerf I think it's important people understand the principle of scaling. For instance, this lifetap nerf does not mean stamina is a detrimental stat. People are saying things like "Now taking a fort buff will hurt me!" which is wrong.
What this lifetap change DOES mean is lifetap will scale negatively. Lifetap will effectively have a worse health/mana return ratio than it would be if we just didn't equip gear at all. To matters worse the problem is compounded when you consider that many gear "upgrades" like season 1 to season 2 have more stam and LESS INTEL. Such is so significant that with the new lifetap change "upgrading" from season 1 armor to season 2 armor would leave the warlock much worse off than before.
Comparing warlock's ability to lifetap to other casters makes no sense either. Across the board all warlock gear involves the principle of high stam, low intel, no spirit and no mp/5. Warlocks are a unique caster because they have no baseline mana return that doesn't cost health. They also have the fewest mana returning talents of casters.
Blizzard says this change is geared towards hurting us in pvp which is idiotic for several reasons. The change does more than hurt warlocks, it cripples them right to the core of the class. It isn't a pvp nerf, it affects every aspect of play. Warlocks are in no way dominating pvp. In fact, arena representation charts show warlocks slipping to just below average while warriors remain #1 in every bracket.