The main reason for this is it takes the guesswork out.

Although you can find all the information about the quests on wowhead if you want to go and look.

It works like this :

1. Speak with XYZ

2. Accept all quests here

3. go to Orggrimarr

etc…

The reason it works so well is because your quests end up being linked all together and you end up handing in about 6 at once and getting loads of XP.

In the time it will get you to 70 Joanna did it in 5 days however you would have to be playing non stop to do this!

I would say if you play for 2 hours a day it would take you about 1 week maybe a bit longer.

Hope this helps.