Terrible Trouble in Tristan - Quest Fail to Update

[Sahji]

This isn't so much a bug as it is a minor annoyance that would be nice to change.

In the event that you kill "Archibald Circumvax" with an elemental, quest journal will fail to update and you won't be able to turn in.

The story as a whole:
Both characters had the quest and had not leveled up within the time period.
Both were in the party from the beginning of the quest, and were in it the entire quest. There were no deaths are respawns.
Archibald was spoken to and battle commenced.
He was killed by a water elemental owned by a character. His undying form was also killed.
Eloria does not offer any dialogue.