Mauls are totally over-the-top on siege. Two maulers on top of a ladder completely lock it down, and can get 15+ kills a round without even having to block once.
To me though, the worst part of maulers is that their weapon is so heavy, they just have to block you once then you are weapon stunned for an eternity. So the oft-repeated mantra of "just spam the mauler" is totally bunk, because as soon as they block you once, your weapon is slower than theirs for the next attack.
I say don't remove crushthrough, but make all weapons with crushthrough unable to block (except chambers). After all, if you use a weapon which nullifies your opponent's blocks, you shouldn't be able to block either. Realism-wise, it's ridiculous to watch someone with a 20 lb rock on a stick parry a longsword/katana all day like they are using a fencing foil.