I know a lot of you have realized that standing on the hill top that's closest to demon spawn turns out to be a bad idea, if the demon spawns, and aggros to a spectator while a hunter is attempting the demon, it will despawn as we've seen multiple times.
To fix this, it's been suggested that you should go stand closer to the cliff sides away from the spawn point as to not have this happen, as well as let the demon path down the path a little bit to ensure no aggro (in case someone's afk).
Another thing that would be very smart to do to avoid any despawns or bad luck, is dismiss all your pets, so there's not any chance of an accidental despawn if the demon does aggro on you, if it detects the pet on its threat table, it will despawn as well. Even if it's just coming after you.
TL;DR
Stand further away from the spawn point, and dismiss all pets.
Thank you!