Aka difference between viable and optimal.
optimal for boss 1 might be 10k, yet your loadout does 8k, the dps requirement is 6k, you are viable.
Optimal for boss 2 might be 8k and your loadout cuz it happens to be optimal for that boss achieves that 8, you are optimal and way above dps requirement.
Blizzard might have a bad name for balancing but they at least balance raids and m+15 (non epeen mode) to be doable by any spec and be viable