I'm not sure if this has been previously stated but the 2% drop rate is just that. 2% chance every time you do a job successfully. This does not mean you will gain one ec for every 50 jobs successfully completed. It's the same 2% chance every time.
I am getting ecs from the job which I haven't completed. Its almost 2ecs per ul from the Vegas Party Job. Also in the ul on the vegas party job I got a DN.