Well, a suggestion... especially for the really large fates, I was with a group trying to spawn cassie for 3 hours in a row pretty much for it then popping with 6minutes left or there about.
Here is the case... we preloaded every spawn of morbols by killing 30 each, at each spawn + whatever else came in the way morbol wise probably ending up with like 2-300 done.
Suggestion goes by if big fate spawns, extend time for everyone by 30 minutes or the likes aka. like how the diadem is when the grand mission spawn, especially Cassie/Louhi and such, as it is simply not fair that a group of peopel that really worked for it then have to give it up to everyone else who is AFK.
Also Add a contribution system, if afk andnot have helped anywhere, you wont get any rewards from fates.