I really despise the D:0 metric.
In my opinion, it pushes front-line staff into making bad decisions just to make the metric. Think about all the times we hear of someone complaining that an aircraft door wasn't held open for "two more minutes," or flights that went out mis-catered or not so clean.
Since the metric that the bonuses being measured against isn't whether or not you made a smart decision that saved the company money, rather that you released the aircraft brakes come hell or high water by the D:0 time, what incentive does an employee have to screw up their station/region/national D:0 metric in favor of the traveling public? Other than, I suppose, not being screamed at or having to do a bit more work to handle re-accommodation. A:15 is a much better performance metric that can encompass good tactical decision-making both on the ground and in the air.