Reposted from Reddit:
In order to get the dungeon master title, you have to do every path of every dungeon. That means all 4 paths of every dungeon except Arah which has five.
The problem seems to be, when Anet retired the story mode dungeon and made Arah story part of the personal story, they also created a new achievement for it and retired the old achievement.
I know this because there are people in my guild who have their dungeon master title, but under the achievement track Master of Arah, they have completed 5/4 dungeons completed. That means they did all 4 paths and the old story mode.
I on the other hand have 5/5 completed because I’ve done the personal story since the changes. So I’m pretty sure the personal story dungeon counts.
The problem is, people who did the personal story at launch and are just missing a single path to get dungeon master, now are missing two paths, because the original story mode dungeon doesn’t count as the personal story dungeon.
Nor can you accompany someone else and get credit if you’re not up to that step. I just had two guildies only missing that step (as far as we can tell) run the Arah personal story with me, and we finished it and neither of them got credit for Dungeon Master.
It seems they have to level a character through the entire personal story again, in order to get dungeon master, even though they both did story mode originally and they did the new “path” again with me.
I think Anet needs to award the achievement to people who have already done the story path, and not make them repeat the entire personal story again. Cause that would annoy the hell out of me.
If anyone has any information about this, please let me know.
Edit: I’ve found others have this issue too, here’s one of the threads…
https://forum-en.gw2archive.eu/forum/game/players/Problem-with-Master-of-Arah-achievement
Doesn’t shed much light on it, but apparently my guildies aren’t alone.