Applications come with varying amounts of complexity. It's not that they are processing applications out of order, it's that some applications take longer to process because they are more complicated. A straightforward application will not take the same amount of time to process as an application that is a more complex situation, has relationship red flags, a criminal record, delays in obtaining certain documents, background checks that take a while depending on the country... etc. When somebody receives DM only has to do with their own application and has absolutely no relation to when anybody else applied. It is not unfair in the slightest. What would be unfair would be some sort of "first come first approved" rule that forced applicants to wait due to delays related to other people's applications and not their own.