Originally Posted by
Ijoemomma
Although possibly true, that's not the correct answer. Sargeras and the legion don't know how to get to Azeroth. They spent forever trying to find it after it was brought to their attention. A portal was opened to them during and they where held back. it's why we haven't seen them since the last attack.
Unbeknownst to greater night elf society, the Highborne had begun communing with Sargeras. The fallen titan hoped to use the sorcerers and their great magic to expedite the Legion's journey to Azeroth. Without a suitable gateway, he knew that traveling to the world would take ages.
--Chronicle