A possible solution to this problem could be to give incentives for raiding or completing higher end duties with your FC members instead of your Static. It's going to be a very unpopular opinion; however, a few other MMORPGs have little programs in place (i.e. currency, items, exclusive things,) that you HAVE to do with your FC.

There is the obvious solution people are going to bring up... "Why don't YOU just find a static of your own?" While this is indeed a possible solution; my rebuttal is this. Why should I have to PuG, if I joined an FC for the supposed community of like-minded individuals? What is says to me, is that they are willing to do the content... with and only with their chosen group; and not with random people in their FC. Some of the community is fantastic for people who are new to content; others are only interested in parsing and will invite you if and ONLY if you have seen a certain phase, have a previous clear under your belt, etc. That old trope of "You need experience to get experience."