Please enable a character that used to be a part of a certain dungeon group, to be able to relog into that group for a certain amount of time after having a DC.
Characters that dont relog, and thus so dont finish the dungeon, should be ´banned´ or timed out of doing dungeons for a certain amount of time.
Add a vote button to end a dungeon without it being finished (so People that think its too hard for their party can end the dungeon without just leaving). In this way they wont get a ban because you commonly agreed to end the dungeon..
This will add a more ´fair´ perspective for a lot of People doing dungeons. While there are too much persons just hopping into dungeons and leaving after dying once..