I don't come on this forum much so this idea might just get brushed off fast, but what about a third hero as the Giant Goblin?
When attacking he could be a stronger version of the normal goblin. Perhaps his special ability could be jumping over/dealing large damage to a wall?
When defending, he could relentlessly hug and protect your storages, like his life depended on it.
Obviously he couldn't be too strong because of his role (focusing on loot).
