http://www.wowwiki.com/Dungeon_Deserter
Patch 3.3.3 (2010-03-23): The Deserter debuff given to players who leave a dungeon prematurely when queuing via the Random Dungeon option has been increased to 30 minutes, up from 15 minutes. The cooldown for using the Random Dungeon option remains 15 minutes.
Вам еще везет, что пока баф на 15 минут, а не на 30, как было на офе времен 3.3.5а.