I don’t think I did Khadgar’s discovery, but I can’t say for certain. I just started with a quest in the quest hub cave. I ended up in the process getting nightfallen achievement, and some of another. However I finally started getting quests for the Suramar achievement. Got just one left after many hours of questing, a change of seasons. Gotta collect lots of ancient mana just to complete some quests.
Sucks that quests don’t indicate what achievement they are a part of. You don’t find out till you’re done with a bunch of quests.
OK I verified that one doesn’t have to do dungeons nor need revered in anything to get the Suramar achievement.