I think the reason is, that the discipline points are only additive in nature whereas F&R multiplies your damage.
In your example only discipline: 110 * 40 = 4400 %
In your example with F&R: 86 * 40 * 1.5 * 1.5 = 7740 %
F&R upps the damage by 1.5 * 1.5 which equals a multiplicative factor of 2.25! You can bet that someone of the pros (and possibly non-pros) already calculated different build setups including one with increasing discipline points. The only real alternative for an UE Demonhunter is the Endless Walk Set (Compass Rose and Travelers Pledge) which is about on par with F&R concerning the damage. It's slightly weaker but has some other advantages. There are comments in the discussion area of the UE build.