Accepting the fact that when dealing with any government agency here may require some greasing of the skids is key. Law firms, agents, representatives et al abound to "expedite" government transactions. Like any enterprise, immigration agents vary in quality and the amount of required docs they actually prepare for you but their primary function is to act as the middle man to pass on tea money.
In your case, continue without an agent and after much frustration and time you will likely get your visa but even though you have all the required documents, an agent is the way to go mate.