Since the update I am no longer getting credit for health the wraith spell steals. Being a Death school wizard, and having equipped my spell deck with numerous Wraith spells this is a big deal for me.
EDIT: After further play I have found that I do receive credit for the health the Wraith steals, however only after everyone has finished their turn, and only if at least one enemy remains alive. If all enemies have been killed in the same round I use my Wraith spell I do not receive credit for the health the Wraith steals.
I have this problem also and yes you do finally get the credit for the health if all the mobs died, but either by going into another battle or beleive it or not logging out of game and back in, (wouldn't do that if soloing an instance though, as you would have to redo everything)
On my death char it's not so bad but on my other chars I tend to use wraith to heal when needed. Luckily so far haven't died because of this. Well death isn't all that bad :)
I have had this same problem and when it happened I was kinda freaked out But then I realized when the turn you use it ends you get the health from it, but if you finish the battle you have to either go into another battle or go into another room. :? Hopefully Kingsisle will fix this.
The weirdest thing happened after I had used the wraith spell while fighting a boss. After I had used the wraith, the boss would cast a spell at me where he would step into the circle and attack me. While in the center, the boss suddenly was surrounded by the graveyard stones from the wraith spell, and the wings of the wraith were visible behind the boss. The boss would attack, but I wouldn´t get any damage. This has happen twice, in two different boss battles