[ТУРНИР-HotA] Hard Choice

Can you suggest how to specifically prevent this? How can you distinguish between taking a dungeon with only harpies and harpies + some other army?

Why would you even want to prevent this? Is it because some players are bad and can't take dungeons, so they want to ruin the game for others? I don't think it's overpowered, as it takes much longer to capture a dungeon in the Dungeon faction than in other factions, and they often don't surrender in the Dungeon faction, so such a capture will only happen in 5% of games in the early stages.