Greetings,
Currently we’ve already implemented a system that will boost the spawn rate of FATEs that have not been occurring, but in patch 2.3 we will be making adjustments to this so the effect is increased even more. We’ll also be making individual adjustments to FATEs, and in particular we will be making adjustments to the spawn location for the FATE “Taken” so that it occurs more frequently.
Additionally as a side note, there have been rumors floating around that failed FATEs have their spawn rate increased, but the system does not work this way.