There needs to be more loot in the single player side.
The goblin villages in the single player side don't house enough elixir and gold to make it worth it to attack them. The amount of elixir you use training your troops isn't even made back when you destroy their villages. It's frustrating, especially since that's all you can do if you're sheild is in place and you're upping your defense.
it would make the game way more fun if the goblin villages had substantially more gold and elixir as they got harder, it would make attacking them worthwhile.