For the vinaigrette, whisk together the mustard, lemon juice, olive oil, salt, and pepper in a small bowl.
For the salad, cut the avocados in half, remove the seed, and peel. Cut into 3/4-inch dice and toss with the lemon juice. If the arugula leaves are large, cut them in half crosswise.
Put the lobster and tomatoes in a bowl. Sprinkle with the salt and pepper and toss with enough vinaigrette to moisten. Add the diced avocados, crumbled bacon, blue cheese, and arugula and toss again. Fill the hot dog rolls with the salad. Serve at room temperature.