I haven't gone into FCoB yet myself but in talking to people that are near clearing it, I get this feeling that FCoB was designed in a way to be clearable by people who are able to get statics but aren't super crazy hardcore into raiding either. For people that really want the hardest challenge possible, there's savage coil. Apparently, savage coil is far more unforgiving mechanics wise and requires people to always be at the top of their game. That kind of difficulty only caters to a MINUSCULE amount of players. Gating the best gear behind that level of difficulty would make it impossible for 99% of the population to even get past the first turn. Rather, SE has chosen a middle ground where the content is designed to be difficult for us average joes but easily doable by those in the top end statics. For the top end statics, SE gives them savage coil to play in.