What do demons have to do with Pit Lords?:) Demons are great as cannon fodder, but if there are few Pit Lords in the stack (I don't know how many are needed for dragons to start fearing them), then the dragons will start kicking them. Therefore, it's better to bring demons with you (if there are enough of them, but in the given example, there are more than enough) and some meat.
That's exactly what I'm saying: demons will act as cannon fodder, and then the Pit Lords can turn them into fighters...;), but of course, demons wouldn't hurt either...:)