Damn, invisible, because of you, I had to check specifically:), army:
60 demons, 20 pit lords, and 20 imps, divided into 4 stacks of 5 units each. We attack. Death Knights kill one stack of imps, Death Dragons kill another, and only then do Green Dragons attack the pit lords...
In general, it turns out that you can quite use pit lords, the main thing is to be a little cunning...;). Of course, attempts to sort troops are not suitable for online play, but the topic is...:)

And in general, I'm not arguing that Utopia should be defeated without pit lords - you just expressed it in such a way that it is absolutely impossible to do this, but in reality, it is quite possible...