Yeah, you want to have your 70's NOT LINKED to your RAF accounts. The reason for this is that when boosting using a 70 which is linked, you do not get the triple bonus XP. However, if the account the 70 is on is not linked (I get my bro to run me) as long as your toons are in the same group and near each other, you DO get the triple XP (it is still modified because you are being run by a 70, but the modifed xp gets triples so you still get heaps more than you would normally).

I hope this answers your question. In summary, for lots of XP, don't link your account with the 70s.