When you allow new enemies to spawn i have noticed that the game usually starts you in the middle of one type of enemy ... it is usually a giant crop of acid, neutral, or suicide. I have played sadnbox and flew out for a long distance and it was just nest after nest of the same type of enemy. I know more enemies can sort of appera if you play it for a long time but there is not real variety in the spawning.

Is this how it is supposed to be? Every base is usually one type of class (laser, poison, acid, etc) ... there are other types but they are also all clumped together in giant colonies .... there is very little variety within bases.

Is this how it is supposed to be?

Yes. I suppose there is some mechanics allowing only these 3 types and going away from start area can't change it as discovering territories applies the same rule as MigrationAI ("AI:Enable Migration in map settings" must be set to On for new factions to be born later). These 3 factions are easily killed with physical dmg - it seems logical. Eventually with evolution progress more dangerous factions appear (after 30-40%): physical, electric, fast, troll, inferno. Later poison, fire. Then (after 50-60%) energy thieves, wasp, nuclear, laser, etc. Some shift takes place and by 90% evo neutral faction new nests will appear very rarely (or don't appear at all).
Also in my gameplays the random factor was very big - sometimes there were not much suicide biters nearby and sometimes only suicide nests were located at some border. Sometimes poison biters are easier encountered and sometimes very rare. Probably world enemy random seed value determines it (I don't know if it is combined with map generation seed or not). One random event can dramatically change factions distribution on the map. I suppose it's an interesting add-on to game strategy - to control and obliterate unwanted factions close to one's walls. Unfortunately Factorio engine doesn't store random seed and Rampant's "anger" in savegames, thus reloading from save completely changes biters attack/build behavior and resets the level of nature aggression.
The faction of nest is not determined by 'builder' biters faction since Veden removed vanilla enemy migration option completely last Spring. Before that vanilla migration led to the same faction bases to appear and only MigrationAI behavior generated new factions from time to time.
Factions do mix, but not always. Looks like random factor. At game start one can see pure faction clusters, but in the end-game they are mixed a lot. Especially when Hive nest appears and produces different nests and worms types around it.
Simple rule - interesting things will start to happen after evolution 30% if you keep all three map settings in turned on state: Migration, RaidingAI, SiegeAI. It happens slowly but it does. New faction nests are triggered by evolution growth, by pollution provoked attacks and by player's aggression (especially strong response in the mod version 1.0.1)

Thank you garrotte, that is a good description.

Yes that was very complete. I did not know that evolution factor influenced spawn types ... I will play around with some settings some more. I turned off the new enemies and just used natural evolution's enemies + the AI tweaks from this mod. I will revisit the new rampant enemies now ...