Rampant enemies and Krastorio 2

[Flubbred]

So I am playing Krastorio 2 with Rampant (fixed) and good portion of evolution 85 enemies are kind of kicking my ass. Or at least my walls. I do have rampant arsenal and modular turrets, alongside with flamethrowers for my walls. The walls are self healing. But it seems that lots of biter have overkill protection? Looking at the biter stats my advanced laser turrets alone should kill like.. all nuclear biters going towards me but they just seem to tank very well. Same goes for poison biters but even if I kill those, they leave behind damaging cloud of poison that damages walls. A problem when you just kill a whole horde. My plan is to research laser artillery from K2, but is there anything I can do until then? I can upkeep the repair costs but it's still kind rough, when a single attack can leave a nuclear biter going through, killing like 50 walls and some turrets.