How bout a new radical suggestion....

If you abandon a duty..... you have to fight your way out of a gauntlet of mobs.... (as if you are actually escaping and leaving a dungeon).

"Screw it, these noobies are horrible, I dont have time for this..... QUIT".... ok well you abandon duty.... but before you get zoned out to the world map..... you have to fight a gauntlet of mobs to reach the actual exit..

Im thinking the following requirements are necessary:

1.) Level sync to whichever dungeon level you were in.
2.) The gauntlet would be a time trial......proportional to the amount of time spent in the dungeon capped at 30 mins
3.) You can not re enter the real world until the 30 minutes have expired
4.) a treasure chest will pop at the completion of the trial, and the value of the loot will be reflective upon how many mobs killed (this way its not a complete waste of time)
5.) The abandoned party can get a buff of some sort scaled to how the abandonner is doing in the gauntlet.

I know it sounds silly but think of it this way..... The tank leaves 20-30 minutes into Stone Vigil..... well he has to fight his way back OUT of Stone Vigil.... he can run this 30 minute gauntlet killing as many mobs as he can SOLO!. Lets say he clears 80% of the mobs, his treasure chest would loot a green piece of gear so at least it was worth his while.... Meanwhile the party that was left to fend for themselves gets a 1% damage buff for each enemy killed, hence getting more powerful while the tank tries to escape. Everyone wins, and at least the abandoning tank is free to do solo content for the duration.

The person abandoning the dungeon can not sit in town crafting waiting for the lock out to expire/spam mor dhona, or do other productive tasks. He actually has to fight his way out, which would be a punishment in its own because it would be a dull grind your way out. If the tank chose to log out.... well thats his own perogative, and still wont escape the dungeon until the 30 mins are expired..... And more importantly if the abandoner decides to continue playing, at least his progress in the escape is buffing those that were left jilted at the alter.