As a late contribution to the discussion I would like to give some probably irrelevant points:
About the numbers I allow myself to make a little reflection: In the medieval context the maximum recruitment (by this I mean
in times of war) between nations is equivalent to 1-2% of theirs population, so it´s said that TLR and the Ministry of Steel can raise an army of 1 million
of soldiers if they wanted to. Considering Roshar has more population than TFE it should exceed its numbers by far, but one thing must be considered: the majority of the rosharian population is concentrated in the west, noted for its low level and number of soldiers compared to the bellicose Vorin Kingdoms (an exception would be Azir for example because can reach a standard number). The same would apply to the Terrisan population in TFE. 300k koloss would finish balancing in terms of pure number and perhaps due to authoritarian nature of TLR government could recruit many more skaa, something that except Alethkar and Jah Keved (perhaps) no one in Roshar can do.
That it´s possible to recruit much more in Roshar is true, but they would be soldiers as poorly trained as those of TLR and even perhaps physically weaker and demoralizable given their pacifist culture and low gravity environment (considering that it´s said of the skaa that are harder thanks to the physiological intervention of TLR and have rioters among their mistings).
Another issue is that Scadrial in fact does have military generals, although obviously only theorists/academics. Even during the siege of Luthadel
an effective command could be sustained by resorting to the inexperienced nobles and their inherent authority that although inefficient serves to create a command chain.
This is the case of the obligators who studied ancient military theory, logistics (in the army of Straff during TWoA there is a good example) or they simply have some strategic inclination like Yomen/his advisors with the catapults tactic during THoA. Also, I think I remember that the image of Durrand Erikeller shows him leading an army in battle in Mistborn: House War, indicating that there may be nobles or even entire Houses inclined to militarism (of course they must be very scarce given the prolonged peace). It´s obvious that there is a lack of leadership in the front, tactics and command, but that can be compensated with some thugs acting as seargents (with being noble and having messengers already have half the work and authority assured) along with large numbers of rioters and soothers.
