i think gather your party mechanic isn't a good one.
for a start, while people may die for stupid reasons... trying to get their stone can lead to more death...
i usually prefer to finish the quest first, then risk a wipe just to get a soulstone.
the mechanic can also lead to griefing on purpose or not on purpose like when people go afk even for half an hour.
the only real solution right now, is just to memorize these kind of quests and just do them solo or with trusted people.
which has the negative side effect of making these packs much less posted and in general reducing the number of lfm.
the quests i found so far are:
2) misery peak
4) come out and slay
5) party crasher
5) the snitch
12) droam quest
they can easily be a huge royal pain when someone decide to afk...