To me the Legion invasion appears to be on the contrary = that Azeroth is actually invading Legion.
Yes Legion is appearing on Azeroth in attempts to get control over Azeroth, but since invasion zones are so overcrowded by players, poor Legion forces have barely chance to get anywhere further then just few steps from their Command ships, Portals or whatever sources spewing out demons in attempt to actualy build up worthy army and engage on Azeroth properly. Legion is getting heavily counterattacked back right after they land and have chance to suck on Azeroth's air. And than Azeroth forces (mostly presented by players in raids) are invading Legion ships, tombs and overall places to not just stop Legion from doing it, but to invade them deeply and stop Legion for good.
All of this seems to me boring. Why? Because I have the feeling of being super strong hero in a group of another strong heroes which stops nothing from achieving whatever Khadgar gets on his mind. Why forces of Azeroth never fail? Why aren't they getting crushed, killed most of them and scattered around and Blizzard making another expansion sort of an uprising, from those who survived (obviosly players mostly). So we scavenge out of the bottom of the grave and rebuild Azeroth or even exile Azeroth as Draenei were forced to from Dreanor? This might give us the feeling of the new begining.
THIS slaugther happend BEFORE the Legion expansion came out. 2.5 milion Legion invasions repeled! I don't want to even imagine how many demons have been wiped out this way. I bet they are runing out of demons.