I have joined so many In the Belly of the Beast pick up groups, most of the time I get lost in there.
I think 7 out of 99 I managed to get there, after that I just gave up on the quest.
Btw, cogs quest seem to have the same problem. There are a lot of them that are faster to complete than it takes me and a bunch of others to get there.
Esp if you fall into the lava because of lag and have to run again as either death or no way back up.
Other quest:
The island in IQ has a hard lock out, but I think you can use a friend teleport to get there. I count the whole pre-quest as run to quest time.
And by that standard a whole bunch of other arcs do as well.
Bring me the head of Ghola and that other quest out there, stupid long run time and you can get lost easily as designed to do just that.
King's forest quests, long run time to unquiet graves, lost thread, the port point and underdark entrance.