In a small bowl, dress the arugula lightly with vinaigrette, reserving the remainder for the tomatoes and oranges. Season dressed arugula with sea salt and pepper to taste. Set aside. Arrange tomatoes and oranges alternately on a chilled serving platter, or 4 chilled salad plates. Drizzle liberally with vinaigrette. Distribute the dressed arugula, olives and feta evenly over the plates. Sprinkle with tarragon leaves or basil. Season with sea salt and pepper.
In a small bowl, mix the vinegar, orange zest, Dijon mustard, honey and shallots. Slowly whisk in the olive oil. Season to taste with sea salt and freshly ground black pepper.