@Mykan
I shifted towards a single factory in each tier during chapters 4 and 5. I had considered going to a tier 3 only design because I could see the personal advantages, but after reading a number of topics here on the various costs I could not inflict that on someone. And so chose to keep 1 factory in each tier, and to make fair cross tier trades if I became desperate.
Until the end of chapter 6, eight L15 workshops, L2 Endless Excavation and L3 Tome of Secrets was plenty to fuel my factories and my military. Excesses would occur regularly because of reciprocal helps; during chapter 7 all the previously excess supplies shifted to being used to produce military. At the end of chapter 7 I increased my workshops to 10 but retained the L15 aspect for all of them. The increase was to cover the orc requirements and because many event quests aligned upon a multiple of 5. Adding 2 workshops takes the same space as upgrading 8, but the time required to start obtaining a return is lower. At the next stage I will upgrade the workshops.
I ran at 3 armories for a time, but because that did not keep up with a 6 hour sleep cycle I have increased my armories as I could spare the space. I currently stand at five L20 armories. The increase of 10 troops per training, to upgrade to L21, is inadequate to justify the costs to upgrade. My barracks is always maximized as fast as I can get it there and a training grounds acts as back up to assure units are being produced constantly. I currently have a L4 Needles of the Tempest.
On the recent edge I have been pushing upgrading housing, upgrading armories, and building the orc settlement. Doing all of that at once has pressed my supplies towards 0, but the Edrasil event provided me with numerous +15% supplies instants and I have used a few when things got tight.