Ice and Fire

Subordination, perhaps.
You saw the screenshot I posted. By the time he reached the dwarven castle from the garrison, the number of Jarls had increased to 152, and the same happened with the other troops – there were 1600 harpooners. These Jarls are only subdued by 0.01 turns by succubi =)). Letting them cast a spell means losing a stack immediately (minus the succubi – they attack them). In principle, if you target an artifact that reduces defense, they might survive a turn – the subordination and this magic will then affect the computer. Then just attack everything that moves with them, while simultaneously casting a dispel on the archers (not a mass dispel, so the Jarls can retaliate). When they are defeated, move on to the next stack.
With this setup, yes, it's viable.
By the way, can you get subordination in Utopia? I farmed it for the second time – it gave good artifacts + 3 spells (shock, holy word, and some other).