As for why Black could win against Callow. The Calamities. They directly got their fame from the fights there.
Warlock personally killed the Wizard of the West. Captain will shred small armies though attrition in the night.
Assasin, well we have seen how effective it? is. Goodbye officers and mages.
And Black himself has aspects designed to argument an entire army.
I think we agree, the later powercreep in ridiculous Named powers makes armies moot, when warlock can call down meteor strikes to level armies and fortresses. Not to mention cat dropping iceblocks and lakes. Or kairos using a thunderstorm to wipe an army, ...