In small bowl, combine red wine vinegar, crumbled feta, 1 tablespoon lemon juice (half lemon's worth), garlic, dried oregano, salt, pepper, and olive oil, whisking until ingredients are fully incorporated. Taste and add more lemon juice and/or salt as desired. Set aside.
With sharp knife, carefully cut tomato into 6-8 wedges. Place wedges in small bowl and pour 2 tablespoons of prepared vinaigrette over. Toss to coat tomatoes in vinaigrette then set aside.
Pat shrimp completely dry with paper towels then place shrimp in large bowl. Add blackening seasoning (plus salt if seasoning doesn't already contain salt) and toss to coat shrimp in seasoning.
Heat large skillet over medium-high heat. When pan is hot, add olive oil. When olive oil is hot and shimmery, lay shrimp in skillet in one even layer. Cook shrimp 60 seconds, then carefully flip shrimp over and cook another 30 to 60 seconds, or until shrimp just begin to turn pink and curl slightly. Immediately transfer cooked shrimp to bowl or plate and remove skillet from heat.
Fill serving bowls with equal amounts lettuce, then top with artichoke hearts, crumbled feta, kalamata olives, marinated tomato wedges, and blackened shrimp. Drizzle vinaigrette over top of salads and serve immediately.