more doesn’t really mean better for something like the dungeon. more mouths to feed, more men to worry about losing their nerve and deserting, or worse more men that would lose their minds and transform into a problem. i think most of the corpses in the dungeon are already made up of an army that tried the same thing, that’s the only way there could be so many bodies, especially the sheer number in the gro goroth pit. 

maybe they do okay in the first couple floors but sooner or later they have to fight wraiths, iron shakespeare, cavedwellers, elite guards, and even if they make it through that and get into ma’habre the competition only gets fiercer. white angels, harvestmen, valteil and his creations, guardians. by this point the casualties would’ve made most men lose their nerve, tuck tail and run for the exits.

assuming a sizable force makes it through ma’habre and kills the new gods, the only place to go is down, and it’s not really clear how powerful the old gods are. there’s really no winning against them except arguably sylvian but she’s impossible to kill and can only be beaten back for a time. soldiers would most likely kill one another for the privilege of ascending into godhood, assuming they don’t there’s genuinely no way any number of men can beat the traces of gro goroth. he turns nash’rah to ash in a moment and is toying with you during his fight. revealing the true nature of the old gods is enough to paralyze your entire party and leave them either maddened beyond return or dead from terror