Due to lack of sufficient players during Temple of Dwayna events, NPC Historian Vermont had died after succeeding Defeat the Risen Priestess of Dwayna event.
He had died at the inappropriate stage of events by the remaining risen mobs and disappeared from the area, causing the meta event to halt indefinitely until the next server reset.
UPDATE: Since the recent game updates, this should no longer be an issue.
UPDATE: Nevermind. NPC still dies and halts the chain event on the same condition.