I haven't played D&D since it was AD&D 1st ed. But my understanding/memory is that Resurrection reconstructs the mortal body and restores the soul so you can cast it on any mortal remains (corpse, ashes, bones, etc) and get a living person. Any maladies (including vampirism) they had are removed in the "rebuilding". Durkon offered to destroy and Resurrect Malack a strip or two back (when he was winning the fight).
It's different from the lower level "Raise Dead" which simply returns the soul and hence requires a pretty fresh corpse. And a means of healing their cause of death upon being brought back to life.
In one of the strips, Roy asks Durkon during a battle if he has a Raise Dead memorized and Durkon says no because it's hard to cast during battle and the dead don't get any deader if you wait a day. Had Durkon been available immediately after Azure City he could have probably Raised Roy. But the long wait while Roy decomposed meant he needed a Resurrection.
Wow. Regular ol' Joph fan club in here.