You're not very perceptive, are you? Pit Lords, in small numbers, can serve as cannon fodder themselves. Dragons don't like monsters with special abilities and try to kill them first: vampires, crusaders, pit lords, shooters, etc. (they only fear Gorgons, and not always). Moreover, Pit Lords have a low amount of HP. And if there are only a few Pit Lords in the stack, dragons might mistake them for your own units and start attacking them in the first round (at least in my recent game, they started with them; maybe it's not because of that, maybe I'm wrong). And you need to protect them. And having only Imps as cannon fodder is not enough. Even if there are a hundred of them, it won't last even one round. Units from levels 1-2 from other castles will be used as cannon fodder.

Great poem!