Mix all ingredients in small bowl. DO AHEAD: Can be made 1 week ahead. Store airtight at room temperature.
Cook bacon in large skillet until crisp. Transfer to paper towels to drain. Break in half. Gently mix chuck and sirloin in large bowl. Form meat into 8 patties, each 3 1/2 to 4 inches in diameter and 1/3 to 1/2 inch thick. Using thumb, make slight indentation in center of each burger. DO AHEAD: Burgers and bacon can be prepared 8 hours ahead. Cover separately and chill.
Prepare barbecue (medium-high heat). Sprinkle 1 teaspoon coffee rub on top side of each burger. Place burgers, rub side down, on grill rack. Grill until slightly charred, about 4 minutes; turn.
Place 2 bacon slice halves atop each burger. Cook 3 minutes.
Top each with 1 cheese slice. Cover and cook until cheese melts, about 1 minute longer. Place burgers atop bottom halves of buns. Top with onion slices and tomato slices.