I don't know, maybe I'm just not getting it? I didn't start a new game, I just loaded my last save in the Campaign (the "Forward and Inward" mission). It was near the end of the game, I played until month 25, gathered all my troops, and at the same time, the number of neutrals became disproportionately large (maybe it's a bug?). There was no way to win. There was a Castle of George nearby; it had a large army, but not large enough to earn a decent number of points, and waiting for it to build up a decent army with just one Castle would take not 25, but more like 250 months.

This isn't a bug; I ran into the same thing. I waited for so long, hoping that one of the heroes would have 200+ champions, and the other would have 400+. Then I looked at the map... "High," "Deadly," and in some places "Medium" difficulty. Hmm. I managed to improve the Dynasty weapon on "Medium" difficulty, but I was surprised by this situation.

Then I realized why this happened: the hero's army grows by +n per week, while the neutrals grow by +n% per week. I calculated the percentage for the Archangel's army – it was 17%. Therefore, the neutral army increases much more each week than the hero's army.