Killing Pazuzu and leaving in hopes to join a new instance won't be a thing if instances aren't full, as you'd likely join the same mostly empty instance you just left.
So they'll either join, kill Pazuzu and leave without coming back (meaning that the instance won't scale up for more than 10 minutes), or they'll do lower level Fates while waiting for the next window.
That's a git gud issue and common sense of not fighting things that may make you wipe. Besides, you won't have to deal with bad culling or idiots pulling random trash to the group, making fates way easier.
And even if you do wipe, all it takes is one person to take the penalty and come to raise the others. Sucks for that player, but it's not the end of the world. And if you took a played below 6, then no penalties for you as long as that player has a job able to raise or a phoenix down. "DEVASTATING" is not how I would put it.
Anyway, you are not giving me the feeling that my points were reassuring at all, so I'll take my leave and simply say "let's wait and see".