Hi,
the party system issues seem to be deeper than buff issues.
Into 99 (Ice blade plateau), 100 (Sun temple of eternal sleep), 100 bis (Tomb of souls) (easy, normal or hard mode) dungeons, the one who first kills a mob is teleport outside just after the mob dies. This unlucky one is teleport outside the dungeon or at one of the previous place he teleports...
We try with two or three people on Nuada server and stop the tests for it was expansive in teleport stones...
The one who stays in dungeon earns no experience or skill points...
If you try to come back you are no more in the same dungeon than your partner...