If the new healer attack from healing via 2 GCDs is a gain instead of dps neutral, then we can see this as a potential balance problem. If its not a dps gain for a healer then we can see this potentially as a possible for DRK who would get greedy and then die to auto or raidwide because they spammed it.

If they brought DRK hp sacrifice from PVP then you would have to bring back things to compensate that like Soul Survivor and shorten cooldowns on Carve and Spit and abyssal drain. There has to be a balanced way to heal that damage you are causing which is why it will be interesting to see which route they take.