How on earth does this still exist as a problem? I joined a dungeon group which had kicked a previous member, and was unable to join. So I figured "oh maybe he's still porting out, I'll wait 2 minutes" - same error. Then, I tried changing zones and still the instance was full!
Finally, the group kicked me because they had been waiting 5 minutes for me to try and join. I don't blame them for kicking me, but now I have to wait another 10 minutes before I can even try and rejoin another group. ZOS please, please, there's still minutes before the patch! Fix this *** problem that's probably been there since group finder was implemented, just buried under the host of other problems which have been resolved. I shouldn't have to troubleshoot your game for you, and players especially shouldn't be punished if they never even make it into the dungeon!