The ACW not humanoid - the point I was trying to make is that Skullcrusher has other things going for it even if the monster in question isn't humanoid. Though I didn't know that the Wyrm's mindcraft is that weak; I knew just having the water orb meant you were pretty much safe from it entirely.
With the ACW, I think which melee weapon you're using is less important than making sure the wyrm is appropriately disabled. It can dish out the hurt at ranged and in melee if it's in possession of all its faculties, but get some confusion, blindness and poison in there (or even paralysis), and Skullcrusher deals enough damage in berserk to get the job done with ease.
I quite enjoy the thought that I might make Grand Mastery on a melee weapon again one of these days, so I usually decide on one weapon to use, and Skullcrusher does really well on average thanks to the absolute murder you dish out on humanoids. It's never happened to me that I found Skullcrusher, specialized in it, and seriously regretted it. Of course sometimes you find Executor in a greater vault on D:47 and feel kind of bad that your Axe level is still 1 from Bart and you're not laying the smackdown like you could, but that's not anyone's fault.
EDIT: Oh, and about the IGB - I can't say anything about its accuracy because I haven't read it. I see no reason why the information Pavel has researched has to be added to an unauthorized alternate ("improved") version of someone else's work rather than a document of its own.