Bring all ingredients to a boil in a medium saucepan. Reduce heat;simmer until slightly reduced, 8–10 minutes.
Let cool, then strain into a jar. Cover and chill.
Combine tequila, Campari, lemon juice, lime juice, and shrub in a large pitcher.
Place 1 1/2 cups tequila mixture in acocktail shaker; fill with ice. Shake until frosty,about 30 seconds. Divide between 2 rocksglasses filled with ice; garnish each with alime wedge. Repeat 3 more times.
DO AHEAD: Tequila mixture can be made 6 hours ahead. Cover and chill.