Hi! I liked to play vanilla factorio with death world marathon (both crafting and tech 4x expensive) and with nests 600% and expansion rate at max. It was a challenge for the first tries, but then the game became easy. Also, I became bored with the way that the game becames easy when I got to 100% evolution and even behemots could nothing against two laser turrets rows.
I then installed rampant fixed (disabling nukes and suicide bugs, as I've read online they're just annoying and very hard to counter). I managed to survive for the first 5 hours. Everything was good, biters were different from the vanilla ones, maybe stronger but nothing that a row of turrets couldn't stop. I was planning to get ready to defend from big bugs at evolution 2.0. And then regenerative faction attacked.
Every bug is like 10x more resistant than the others, sure they're slow but they consume all my magazines on them. Moreover, water is far from the base: I pump the water from the lake and move it with pipes. A bit of turrets around the pipes could stop attacks on them, but with regenerative they simply walk past the turrets destroying the pipes sending my base always black, stopping magazines production.
All of this happened in a matter of minutes: my base was well defended, and with a single bug spawn (thats way stronged than normal bugs which spawn at 0.2 evo, and they spawned at 1.7) everything is going down. They're vulnerable to fire, but due to the expensive mode I'm far away from the flamethrower tech. I don't want to change settings and make them easied because I love the way you have to defend and plan everything, and kill every single nest you find around when expansion phase begins. But if a single upgrade to the enemies causes that much trouble, I wonder if that's even possible. It would be easier if they didn't randomly attack pipes sending my base black, I could just increase magazine production and research turret damage and attack speed. But this isn't the case and the pipes can't be safe. I can't even build a wall of turrets around them: it's too late, base is simply not producing anymore and I can't keep with all the attacks at the pipes. What can I do? Is there something that can kill them easier and in early? Any way to stop them from attacking my pipes?
Thanks! The mod anyway is great, I love challenges.

Regenerative biters are designed to give the player an incentive to use flamethrowers. Otherwise, although they cannot kill, they drain defense. However, this becomes true from level 4 and above. Before that, they are weaker than average biters.

You need to change the settings of your game. I recommend trying the standard deathworld first. Even there the player will not always win
Also, according to my solo games, the death world 600 * 600 * 150 is already close to impossible - it requires dozens of save/load, including rollbacks of 2+ hours in order to fly away.
If you have Rampant Arsenal, the late game is easier, but still hard

Regarding the pipe attacks. Biters seek, find and destroy most unprotected objects. This is a feature of the mod. If you cannot protect something critical from them, you are guaranteed to lose.

Hmm.... Then I should be able to restart and resist past the 6 hours mark. I'll not leave the challenge xD losing is part of the experience. I'm really worried what's past level 2... If level 2 hitted me that hard, other levels might delete me even before.
They spawned before evolution 0.2. What causes them to spawn? Time? Pollution? Both like normal bugs? I wonder if I speedrun production and research if they will just spawn before.
Also, if I reduce pollution (with siege and raid player settings on) will they attack only with pollution just like vanilla game?