I am a level 74 and in Dalaran right now. I click on the Adventure Guide and click Sholazar Basin and it gives me a starting quest to talk to Archmage Pentarus, but when I accept the quest from the Adventure Guide I cannot secure a flight to Sholazar Basin. I have to abandon the quest from the adventure guide and go directly to Dalaran in Northrend, and therefore start the quest for Sholazar at the Dalaran landing pad.
Archmage Pentarus is there ready for me to start Sholozar, but if you try doing it through the adventure guide he will not be targetable for any departure for the quest.