As with any discussion of Classical texts, I believe you will find different positions and answers to such questions. I am not sure it benefits anyone to take one or another as "the answer." Rather, it is the widening of discourse that is vitally important to such queries. In this, I see dharma as playing a larger role inThe Ramayanathan it plays in the narrative of Shakuntala. In my mind, the adherence to the law or the established rules of conduct are shown inThe Ramayanato exact a greater toll on the lives of the individuals. In this, dharma plays a larger role because it shows how difficult adhering to such rules can actually be, and in turn justifies the need to live in acccordance to dharma. The narrative of Shakuntala does display the importance of dharma, but not to as great of an extent that it is shown inThe Ramayana. Dharma and strict following of it plays a role in all of the action and conflict inThe Ramayana. From the exile of Rama to the battling with Ravana to the rejection of Sita to her walking through the fire are all caused to the adherence to dharma, the expectation of natural law. Without this dharma, these events do not happen. They come at great cost. Dharma is what causes Rama to distance himself from Sita and dharma is what compels her to display her virtuousness in walking through fire. There is very little else as difficult and through this, one recognizes how difficult adherence to dharma actually is, justifying its importance. While dharma is present in the narrative of Shakuntala, it does not carry the same level of expectations and cost than in the narrative of Lord Rama. I think that this is where dharma plays a larger role inThe Ramayanathan it does in the story of Shakuntala.