Planetary Defenses seem to be researched correctly with the mod - the example above seems to be simply due to the fact that the AI hasn't gotten around to them yet.
It is a classical case where the AI only knows the player and declares early war due to its opportunistic logic. The other two AIs are probably building up their forces in their respective regions so the game should be worth continuing
As for difficulty:
- Humans are the most difficult faction to play. Yoral are around 2-3 easiest race due to their planet preference, production bonus and wide array of tactical destroyers (including the most powerful early-mid-game ship the Torpedo Destroyer)
- Enemy Imperials are in a disadvantage as the AI does not know how to take advantage of the stargate (the primary benefit of that race)
- Boxed map contains corners- use oval shape instead do create a more open map where there are no safe corners
If you really want a challenge play as Humans against 4 Yoral with 50 stars
as always, Normal difficulty should suffice with the mods
While it is true that the AI has difficulty recovering from major losses, this is true for the player as well. Didn't particularly see anything where it could be further improved upon if we are not counting diplomatic actions including hiring of mercenaries. The AI does a great job at preserving its ships and building new ones. In my last game I have seen a Gremak empire being beaten time and time again and it was constantly coming back with a fleet of light and heavy cruisers and some destroyers and taking back planets from the enemy even though it had no chance to put up a real fight - works brilliantly.
Haven't seen a case where they would produce troop ships though - maybe these were issued for production before they have lost their fleet(s) and the AI decided to just finished them instead of changing to combat ships right away...