Inferno tactics.

Yes, during a siege, you can use Wait on the Devils so they aren't killed immediately. I agree that it's difficult for Knights to defend against a Castle, but letting the Demons take the damage and then turning them into Goats, or preserving them to absorb damage, is a good strategy. Use the Gogs to cover the area, and gather a group near the passage so that the Gogs can attack multiple targets, and the Cerberuses can help. With the Devils, you can take out the Monks more effectively, as there are fewer of them, and they only shoot once, but they have much higher HP and damage than the Archers, which always compensates for the difference in numbers between Archers and Monks. I don't think anyone will send Devils directly to the Archers, unless they're suicidal. And if the Efreet and Archers are only in the enemy's ranks, you can use Wait on them. The Efreet will take out the Monks, and the Devil, for example, can take out the Archers, preventing them from using ranged attacks and allowing the Gogs to survive longer. (IMHO, it's a bad tactic, but who knows?)