Balanite, I watched your video and was amazed at how very much exactly the same you and I start out. I guess it is a testament to how tightly balanced the map is that two random people would be nearly click-for-click identical after (in my case) ~20 hours of failure.
I had the idea that maybe there was a way to game the mechanics of the spiders by spreading out the brood chambers to split as many spiders off from the main group as possible, but it wasn't until I saw your video that I actually tried it. (I really felt strongly that I shouldn't need to).
Compared to your video, the third spider wave of night 2 I actually had a few more ants than you did, but still was rolled over like they were nothing. Yet you handily defeated them. Even with my brood chambers spread out all over. I cannot understand exactly what is happening, why do I fail so hard there?
I noticed (this may be purely animation weirdness) that the spitters seem to stall out, it looks like they stand around doing nothing, and occasionally spit once. Almost like they are firing at the same rate of a mortar ant. This complete lack of DPS would explain why I can't kill very many, but I would expect if that were a genuine bug, that everyone would be experiencing it.