Working on Secrets of the First One (achievement 15259), the quest line up to Arbiter in the Making (quest 65328) is required to complete the step A Means to an End. During Match Made in Zereth Mortis (quest 64889), Between A Rock & A Rock (quest 64935) becomes available, which does not need to be turned in to get A Means to an End (achievement 15518). However, if one gets the achievement without turning in the quest, (1) the campaign progress UI never acknowledges the completion of the achievement (even though the achievement is marked as completed in the achievement UI), (2) the quest can no longer be turned in because the NPC (Pocopoc) is no longer registering as a recipient of the quest, and (3) the Blizzard map shows a turn in location that was relevant during the quest line, but no one is there any more.
And, as you may guess, even if one continues to complete Starting Over, the campaign progress UI does not register that as complete either if A Means to an End is not showing as completed.