In the commited version of the Danubius map D204, there are way too few gaia attacks. In a recent 4v4 test, some players were not even attacked a single time, most players only 1 to 3 times (within an hour gametime).
This was mostly because in the balancing of the time when the map was called Danube (see old balancing file),
people have suffered a lot when they tried to cross the river, because

• The ships respawned very quickly
• Really many ships spawned (up to 3 per player and that number includes gaia, so 8 players = 27 ships all 5 minutes)
• There is a negative feedback loop: Either it is easy to beat gaia ships, then everyone beats it and gaia doesn't appear at all. Or it is too hard to beat gaia ships, then noone does it (economically not advisable), therefore the one trying to cross will get all ships for those 8+1 players.

• Furthermore there is a bad sideeffect of setting the stance to "violent", because the targetAttackersAlways property that is only set to true for violent (see UnitAI.js) means that
  • Ships will become stuck at the shoreline trying to attack towers that are out of reach, when they mostly ignore them when having aggressive stance. Therefore most ships would become destroyed by towers and therefore never ungarrison.
  • Rams will attack the infantry once attacked, thus ignoring the CivicCenters / Towers almost entirely

The nerf in the committed version was way too harsh.
We (siole, Hannibal Barca) decided it would be better to have players having to struggle for a significant time of the game (45min) than to not have any noticeable gaia at all.

Therefore proposing to move to "80%" of the difference in the prior and current balancing into the direction of the prior balancing and revert the violent stance.

Also fix the class matching, as reported by bb:

2017-04-19-QuakeNet-#0ad-dev.log:22:53 < bb_> elexis: tracked down some of the formation bug: matchesClassList doesn't take "-" things as an option it reguires "Unit+!Ship". Testing with that is better but doesn't solve all cases it seems

Also as proposed by causative, increase the distance from the islands to the shoreline briefly, so that it is easier to maneuver ships.

If you want to test, start a multiplayer AI game without assigning yourself and make sure that petra AI (potentially very hard with deathmatch resources) is still able to cope with gaia
(because the map should be interesting in singleplayer too). Press F9, type Engine.SetSimRate(20); to fast-forward.
In order to test the stance, let a ram attack the CC, then attack it and see that it works with the default stance, but not with the violent one.
In order to test the islands, start atlas and see that on tiny maps there are no towers, but still an island and on small maps, towers appear.