Go to Amber ridge and get the quest ' Monitoring the rift Sundered chasm.' (if its not the quest its the one beside him that gives you the De buff).
Then after you get the De buff, abandon the quest.
Then if it all worked like it worked for me the De Buff should stay.
PROOF:
http://i411.photobucket.com/albums/p...g?t=1228268956
http://i411.photobucket.com/albums/p...g?t=1228268985
http://i411.photobucket.com/albums/p...g?t=1228269000
Made pics bigger.