After waiting for months to get this final achievement, the latest update on August 5th finally updated this!
As of the latest update, the achievement description has been changed from "
Complete 5 missions for a Clan that then wins a contested Dark Sector.
" TO "Complete 5 Dark Sector Missions.
"Technically, this can be completed in less than 20 minutes if you quit each mission as soon as possible and you can steamroll lower level enemies!
Thanks to the commenters(Geoffistopheles, x CreaM v
) on this solution that there were good missions on Earth, I finally got back to updating it. From what I just tested, I was able to complete a Dark Sector Excavation on Earth in about 4 minutes, from the start of the first loading screen, to mission completion. Also, I had to remember the controls so I was a bit clumsy too! This appears to be by far the fastest method:Mission: Dark Sector Excavation
If your gear isn't up to it for the Excavation, then this mission is a good alternative as you don't have to defend a specific point but can move around a lot more! Also, you only need to go 5 minutes before you can extract so quite fast also.Mission: Dark Sector Defense
If you're interested, here's a detailed listing of my warframe and mods: