[Suzerain of Sheol]

In this setting? Are you kidding? :P

I'd imagine for a "normal" person like he was (no especially strong psychic or spiritual ability), the soul would wither pretty quickly, making resurrection highly unlikely. But for someone with a stronger astral presence, death might not even be much of a barrier (i.e. unless someone hit Shealtiel with a soul-destroying attack, he was always going to come back as a wraith and more powerful than ever, it was just a matter of time. I imagine peak Na'lsa would have been even harder to put down with his Alex Mercer type levels of both physical and spiritual durability.)

But yeah, resurrection can be done since the barriers between the planes are so weak, it just works better on more powerful souls. So unless someone in the group is on-hand to perform an immediate resurrection, most of us would be out of luck.