I don't understand. In the beginning, everyone will inevitably suffer losses in battles against archers or sorcerers (so it's all fair here), but summoning from the abyss is very helpful against melee-neutral units (except for high-initiative units like dancers, as they can reach the summoning point before reinforcements arrive), especially against heavily armored ones. So, what's so difficult about it?
Of course, you need to know the capabilities of initiative to calculate the moves between the moves of neutral units and skillfully position summoned troops. (And they could have made a low-level upgrade that shoots, or at least created jumping demons :))