I'm really not understanding acid damage. I have a Breeder weapon here that is self-described as something that "chews through armor using highly corrosive venom". It does zero damage to Lobstermen. Zero. No corrosive effects. No damage. I've seen similar results with the XCOM acid weapons, too. It claims to be effective against armor, but doesn't actually do the thing it's advertised to do.
You know what's effective against Lobstermen? The Squeezer. One-shots them every time. It's just plain melee damage. It has more of a pre-damage multiplier than the Breeder, but I should not see a range of zero damage to all of the damage between a multiplier of 150% vs. 200%.
The XCOM Acid Gun doesn't even have that multiplier, even though the entry says it "instantly corrodes and damages armor". Stats for Nerds says no. There's nothing special about it, except that it causes Acid damage, and that doesn't seem special enough to cause a noticeable effect.
What is actually the point of acid weapons?
I'm running around in a game without an Examination Room (and thus no sonic), trying to full-clear an alien base to get one, stuck with three Squeezers, desperately trying to corral these super-top important VIPs with the only means to actually kill Lobstermen, because these stupid Breeders do no damage, and my Gauss Rifles only tickle them a little.
And sorry for the rant. The rest of the modpack is excellent. I really like the efforts to put in better in-between weapon/craft categories, and I make use of the surface-only equipment all the time. But, I think acid needs a buff here.