This is unmissable if you are going for "Last Straw", you are required to reach Tier 50 as part of the Fractured Worlds story.

The Last Straw achievement in Victor Vran worth 272 pointsComplete the Fractured Worlds story on Hardcore Hard ModeYou could simply join a friends co-op game who has already unlocked Tier 50 and teleport to them, however you still need to reach this on your own anyway for the above achievement.