This one glitched for me on the latest update. I unlocked all these from around 150 to 500 in 2 minutes. Heses what I think may do it if recreated.
This was on the newest patch, I started to set up a mission from the main screen. I selected halo ce, then the silent cartographer. I then selected heroic then 2 skulls bandana and boon. Then I went to the start tab but didn't starts. This should give you a warning about a skill with a zero multiplier. I then pressed B over and over until I hit the main menu.
This give me around 50 games each. I did it a few more times and the whole set unlocked.
If anyone can confirm or deny this works again I will update the solution. Also if anyone does get it to work again and would like to make a video then I will happily add it.