@Jcho If that's your concern, then maybe you can ask if buster quests are still active in ship 1-3 on the forum? I know in ship 1 before the Bewitched Woods Exploration, I didn't have to wait 5 minutes to see 8 people assembled. But I haven't been playing this mode a lot recently, so can't tell for sure what the current situation is.
Also, besides what's the current situation is, don't forget that the whole situation can greatly change every 2 weeks in this global server. The remaining EP5 contents will be basically new UQs and stories, those won't affect the popularity of buster quest much, I guess. Yet, if they put in some limited time quest, that can affect the number of people playing buster quests.
EDIT: Forgot that endless quests was also an EP5 content.