Combine vinaigrette ingredients in a blender. Blend together and set aside.
Preheat the oven to 350°F and line a baking sheet with parchment paper. Halve tomatoes and toss with a tablespoon of olive oil and a few pinches of sea salt. Spread on baking sheet, cut side up, and roast on middle rack for 20-25 minutes until dried around the edges. Remove and cool completely.
Rub corn with a light coat of oil and grill quickly on all sides, about 5 minutes total; you want the corn to stay crisp. Remove and cool.
Finely chop herbs and green onions (you will have about 1 cup); place in a large mixing bowl. Cut corn off the cobs and add it to the bowl, along with the cooled tomatoes. Add desired amount of vinaigrette and toss to coat. Add salt and pepper to taste. Toss in half of the feta cheese and mix again; sprinkle the rest on top before serving.