I was hoping to get some thoughts on only using Advent colony ships early-mid game. I tried this out and was soon yelling OP during the major battles. Just two progenitors can allow you to colonize and inflict extra damage.  And since your mother ship will be the first to see battle in neutral planets: getting level 3 malice is not a problem.

Twenty-five percent extra damage whenever a nearby ship is damaged, combined with Illum's made for very quick battles. Several battles were ever against multiple players in alliance and about 1/3rd more fleet. Plus, when they are not fighting they can colonize and reduce the cost - meaning more money for your fleet.

I found malice-ing a cap ship and surrounding ships and then focus firing the cap ship often led to half-damage to surrounding ships, even before targetting them.