Another follow up, did the same thing tonight. Erratic spiders spawned, killed all of them, killed first arch walker, killed spawn, killed second arch walker, killed spawn, and the nothing.
Any idea what could be causing this? It's fairly frustrating to have the fairy say it's up, begin the ring event, and then have nothing happen after a while. We did things the exact way we did when the Avatar did spawn, but so far we have about a 50% chance of the trigger mobs not triggering anything.

After clearing the island, clearing the spawn, and such, we went back to check fairy at zone in. Fairy says avatar is still available to kill. We are sure we are on the right island (this is Dust again w/ the spider island in PoAir).
Anyway, let me know if you have any ideas! Or if you need more information.
Cheers