I dont know there are so many threads on this:

How to setup my new RaF accounts (chain or not)

Maybe its changed.

Boosting still works, no doubt though.

I know that this boosting never worked: A RAFs B, and then A tries to boost a character on B. However, if A RAFs B who RAFs C, shouln't B & C get their RAF bonus from grouping even if A is in there with a level 80 character?
Well you would think so. I just tested an unlinked in noninstance and it worked. Let me see if I can test a linked in a few hours.

Ok it looks like it did change and you should be ok doing a chain from your high level account:

RAF Clarification Questions