I've been levelling my last toon to 100 before Legion and I was quite surprised that there are still so many people doing invasions almost three weeks in with 6 of them up at once.
I was expecting them to be barren within a week once everyone had gotten their gear and other unique items. But the high amounts of XP earned has made them pretty lucrative for this whole pre expansion event.
Compared to previous pre launch events, I'd say this one has been a success. Well done, Blizzard.