When I finally succumbed to the FB pull this fall, I put the GPN page in a list rather than having it show in my News Feed, it's the same way I sort 'following' in my Twitter timeline. It's easy to see what KC means since I go there rather than having posts dribble into my main stream.  

Thoughts on the topic...
No question that reminders for shows/presales is a legit usage - some might never know about the shows otherwise. 
Posting photos of special merch available at certain shows is ok with me too.  Although it can be frustrating if you would really like to have something... (as in still pouting over that HOB cat poster)
Obviously Grace's setlists and crowd vidlets are fan pleasers for those not on Twitter. 

But I agree that her tweets and the photos used with the show info aren't enough. It would be nice to see some non-commercial treats interspersed with the 'business' posts. 
That type of content is what makes us so loyal to TIS. 
So, if the FB-GPN-PTB actually care about feeding the fans and want to avoid the work, they absolutely should link/point to TIS on a regular basis. Seems like a no-brainer to do so.