I've never had trouble with RAF while boosting from a linked account. Mind you I set my up slightly different with

A->B->D
A->C->E

It works for me while I'm playing 5 characters of the same level, or while boosting from A with an 80.
Therefore B/C don't only get RAF from A, they get it from D/E aswell, so the A>B>C>D>E with A boosting
shouldn't have a problem with B getting RAF bonus.... "shouldn't"