Returning Armada  may be an ability of the Vasari that is in need of adjustment.

1. Randomization & Frequency

-introduce randomized arrival times for returning elements of the Dark Fleet
-decrease the frequency of such arrivals

You should not be able to rely upon such reinforcements; wildly varying the arrival times throws such reliance properly off. Making arrivals less frequent also makes the ability useful and supplementary to regular fleet construction rather than replacing it, which is too useful.

2. Consolidation

-all assets appear at the same Phase Node (the Phase Node randomly selected per incident of Returning Armada)

It is more of an event when a cohesive single battlegroup arrives, however large it may be; much more playable in large galactic scenarios as well, easier to keep track of.

3. Comprehensiveness

-assets can be comprised of any Vasari ship type excluding capital ships, regardless of the Vasari player`s research

The Dark Fleet would not be limited by the research achievements of the current player, so returning elements of the Dark Fleet should be composed of any ships in the Empire (again, excepting capital ships). This is especially valid when combined with the decreased frequency of this late tier ability, as described in #1 previous. Useful, but not overpowering.