Trying to farm a recipe, I was able to enter Cistern in a private group, as a solo-80.
Cistern has no internal resurrection pad, so i decided to test what happens when i die there.
Even though i had killed the first 2 bosses, and got the message “you are now bound to the instance”, the system kicked me out from the dungeon, and i was not able to re-enter that same instance.
Then i tried the same thing with a private group of 2 level-80s, killed one boss, and then let one character die. After choosing to resurrect outside the dungeon (the only option), it was kicked from the group.
Moreover, the toon that was still in dungeon, and alive, got the message “you need to rejoin the group, or be kicked from the dungeon”. The dead toon was not able to rejoin the group, so the alive toon was kicked out. This happened even if no boss fight was going on.
If group members in Cistern (or Catacombs … or any other dungeon without an internal resurrection pad) die mid-fight … it would certainly add to the challenge, if the remaining persons need to manage the fight and then resurrect the dead within the dungeon … but it might really raise the difficulty to a somewhat inappropriate level.
So, please take this point also into consideration, when designing and fixing the operation of the dungeon mechanics.