Resurrection powers don't work during multi-turn actions
If you are killed in the middle of a multi-turn action (e.g. eating, reading a spellbook), amulet of life saving and the necromancer level 50 power will not save you.
Attached a save. Character is wearing an amulet of life saving and standing next to a hostile greater moloch. Attempting to remove body armor should allow you to reproduce the issue.