Last night when I was turning in my legendary staff I realized you could restart the event over and over again by simply just unequipping your staff. The quest only completes when you have the staff equipped.
To sum it up
1. Start final quest (The Stuff of Legends).
2. Unequip Runestaff of Nordrassil.
3. Let event play out.
4. Go back to Hallegosa and simply just click the start event dialog.
Note: You do not have to abandon the quest to redo the event, and this WILL NOT bug out your quest. I can confirm that this does work.