I pretty much changed all entity groups to .25 and I honestly don't feel like it changed too much. Survivors I feel should be rare, and there are in my opinion too many still.
Here are a few other things to consider:
- animal class and non animal class characters may well be on a different spawning system based on class and not the entitygroups.xml areas they are listed in. Since NPCs are incorporated into animal spawn groups, additional calibrating will help to find the sweet spot. Having an animal with a probability of 9 is unheard for the zombie lists where they are typically 0.1 to around the 1.0 mark which infers a different way of spawning.
- Maxed spawned zombies by default are 64 whereas animals are 50. However, zombies/NPC classes do not have that 'none' of 85 which is potentially an 8500% probability to spawn. It is possible they are overriding that 'none' based on their class.
- The size of the World and the amount of Open Regions will also have an impact. This is the reason the Snufkin Zombies have a default entitygroups.xml and a 'lite' version. On a new world with minimal regions unlocked, those 'Maxed spawned zombies' values will be much more noticeable until unlocking Regions thins things out a little. In addition, it appears a 6K World and 10K World distribute differently with 6K showing a much higher density of entities in one Region regardless of how many are opened.
The NPCMod Core is very much a base for creators to work from, and your feedback will certainly be noticed for future releases, where the template spawns are concerned. The same applies for individual NPCMod Pack Addon creators who will read the feedback to see how things are playing out. While Darkstardragon has also incorporated his 'Raiderz' into the wild animals spawn lists, their 0.1 probability has felt very balanced, and dropping to 0.05 or lower as bdubyah suggested will provide even greater balance where it may feel they are still a bit on the high side. This is a very subjective topic based on each host, and typically the reason for the option to change MaxSpawnedZombies and MaxSpawnedAnimals.
GansSpecialZombies Addon Pack is actually very sophisticated in its approach, by injecting the zombies directly into the default spawning, by using Boe as their feeder. While the NPCMod has been released for public use, there are things that couldn't be comprehensively checked for all areas, simply because each server has their own dynamics and requirements, and there is far too much to check. It will be very helpful if you can also post your findings once you test 0.1, 0.05, and other settings you may try as this will serve as a useful guide for others who may share your specific requirements.