I don't think anyone would intentionally (except for the AI) decide to stand there, unless a catapult hits them and they get stuck in the pit. And if you throw fire into the pit, it will become a grill:D, then the enemy unit will slowly but surely be roasted if it can't climb out, and what effect will plague have, besides the usual damage?
Я - рыцарь, Зверей истребитель!
Я - тот, кто не знает, не ведает страх!
Я - Божий Сын, победитель!
"Без жалости! Без сожаления! Без страха!"