Hey all,
There seems to be a little bit of confusion regarding World Bosses, so here it's what I gather from my personal experience + internet:
1) You can kill World Boss BEFORE finishing the Campaign
2) After you cleared the story, an ICON will appear on where the World Boss is going to spawn (as a Tree of Whisper request, worth 5 points)
3) If you know where is going to spawn, you can join the fight, it doesn't matter if you haven't finished the story.
4) A world Boss spawns roughly every 6 hours (I'll update it when we have an official confirmation)
5) There are 5 locations where the WB is going to spawn:
Field of Desecration, Hawezar
Seared Basin, Kehjistan
Saaran Caldera, Dry Steppes
The Crucible, Fractured Peaks (Beta area)
Caen Adar, Scosglen
Aside from that, WB hit pretty hard, so don't go underlevelled. Use elixirs and incense for a boost of stats and exp and an area boost.
Pray for good people around you lol
Happy Hunting!
Edit: They finally made some precise timer! This is the one I'm using (it also has helltide infos)
https://helltides.com/