Don't think you have a case;
1. Departure delay is more or less irrelevant. Pax should look up the arrival delay.
2. And as earlier mention the delay according Delta was caused by the air traffic controller (contact AESA to find out):

Draft list of extraordinary circumstances following the National Enforcement Bodies (NEB) meeting held on 12 April 2013:

28 Industrial Relations Issues
Strikes that affect the operation of an air carrier. For example strikes undertaken by Air Traffic Control.

29 Air Traffic Management
Where Air Traffic Control suspends or restricts operations out of the airport of departure or into the airport of arrival.

30 Air Traffic Management
Where Air Traffic Control suspends or restricts operations into or out of a block of air-space through which the air carrier must travel in order to operate the flight.