So complicated. I didn't see where in the BatBrain Weapon of the Pastalord handled the splitting of damage, so I "assumed" it didn't work, but I'll admit I didn't test it, so that wasn't right to say.
Saucegeyser does up to 3x damage against group monsters. With my updated formula, WHAM was only predicting 1/3 the damage against School of Many that I saw in KoL. So I figured it had to be the group monster effect was missing. There's probably some easy way to add that, but I don't know what it is.
Just now I did a bunch more spading on Disc Shank. For an AT, there's no moxie bonus, because momentum is zero. The batfactors.txt formula has a minimum momentum bonus of 1 from "max(1,momentum)". Without that and adding knife damage, then things match KoL. The wiki doesn't list a minimum momentum bonus. I don't have a Disco Bandit to test on. I could see it being different there. Of course, BatBrain.ash would need some kind of find-your-best-knife code. I've updated batfactors.txt to remove the "max(1," stuff, since even though I can't test on a DB, the wiki agrees with what I found. That's still not done without best-knife code.