Bring 2 cups water to a boil in a medium saucepan. Add brown rice and return to a boil. Cover, reduce heat to low or medium-low. Cook undisturbed until all of the water is absorbed and the rice is tender, 40 minutes.  Meanwhile, bring the remaining 2 ½ cups water to a boil in a small saucepan. Add wild rice and return to a simmer, reduce heat to maintain a lively simmer and cook (uncovered) until some of the grains start to burst, and the rice is just tender, 25 to 30 minutes. Drain.  Whisk olive oil, vinegar, lemon juice, Dijon mustard, honey and salt in a large bowl. Stir in the cooked brown rice and wild rice. Stir in the currants, scallions and feta. Add pepper to taste. Chill completely or serve warm.