The MMO Genre has never really been about making you engage in Multiplayer Content 24 / 7. Almost all MMO Games have always had large sections of "Single Player" content such as Questing, but it's hard to really check if the statements made by the WildStar team are true or not.
I may not be playing with everyone on my server, but their mere presence does have an impact, it does make a difference. I'm in a large guild, have several friends and I talk with them all the time, and while not everyone has that, the means of doing so are there, so this is more of a choice then an issue as such.