3. multiple priests can use this skill but they each have to cast their own vampiric embrace on the target. and yes it is incredible. the only thing is that shadow weaving cant be stacked double.

When should I use vampiric embrace?

Vampiric Embrace's shared-out healing makes it far more effective for self-healing when you're out of range of any allies. In groups it adds up to a light AoE healing effect; when soloing this can be used to restore significant amounts of health.

Does vampiric embrace heal yourself TBC?

Yes, it does heal you.