It's still moderately useful at lower levels (IA and below), but for higher level players it's pretty useless at this point.
I can't remember the last time a FC prevented me from getting a 5* victory. It's seriously been a long time, maybe a year or so. If anything, with the introduction of the missile silo and having heavies (TDs/generals) deploying away from the main force, this just gives you a place to put them. But it's easy enough to get a 50% QV even without doing that most of the time, since all of those resource buildings tend to be unprotected - especially if the FC is protected.
I've seen higher level players who used to swear by FC abandon it for Coliseum now. Strength of Gladiator is quite useful (and helps you get 50% QV if you haven't already), especially if you're dealing with full SH with heavy air defenses.