Marinade and Dressing:
Combine vinaigrette and mustard ingredients in small bowl. Place beef Tri-Tip Roast and 1/2 cup marinade to food-safe plastic bag; turn roast to coat. Close bag securely and marinate in refrigerator 15 minutes to 2 hours. Stir in honey to remaining 1/4 cup marinade. Cover and refrigerate until ready to use.
Remove roast from marinade; discard marinade. Pat dry with paper towel. Prepare gas grill for indirect cooking by lighting two thirds to one half your grill, leaving remainder off. When grill is hot (10 to 15 minutes), place roast directly above flames. Cover and sear all sides of roast, approximately 8 minutes each. Move roast to unlit area on grid. Cover and cook 14 to 16 minutes until medium rare (135°F) to medium (150°F) doneness, turning occasionally. Let stand 5 to 10 minutes. (Temperature will continue to rise about 5°F to 10°F to reach 145°F for medium rare; 160°F for medium.
Combine arugula, tomatoes, corn, onions and feta in large bowl; toss gently. Place on large platter. Carve roast against the grain into 1/4-inch slices; season with salt, as desired. Top salad with steak. Drizzle with reserved dressing and pepper, as desired.
Nutrition information per serving: 261 Calories; 115.2 kcal Calories from fat; 12.8 g Total Fat; 1.3 g Saturated Fat; 0.2 g Trans Fat; 0.1 g Polyunsaturated Fat; 0.1 g Monounsaturated Fat; 74 mg Cholesterol; 428 mg Sodium; 7.6 g Total Carbohydrate; 0.8 g Dietary Fiber; 25.1 g Protein; 1.7 mg Iron; 402 mg Potassium; 6.1 mg NE Niacin; 0.5 mg Vitamin B6; 1.3 mcg Vitamin B12; 4.1 mg Zinc; 23.5 mcg Selenium; 88.7 mg Choline;