I wouldnt take improved vampiric embrace over focussed mind.
Vampiric Embrace doesnt heal that much and your biggest issue as Shadow is mana, not heal or defensive.
And regarding spirit tab, i dont know, you need to get the killing blow. As twink that isnt so much the problem, but after you kill something you often will have to move or wait so you can sit down and drink anyway.
And i dont know how clever healer are at 49, but when priests or paladins spam dispelll your sw
shadow affinity can also be very good.