For those of you who are not very far along with this grind, make use of the
BC Timewalking event and start the quest chain starting with
友善 on one of your alts. I just tried it and can confirm that the 50% rep bonus applies and instead of boosting you to normal, completing
灵翼之盟 gets you
straight to revered (+63 000 rep). I didn't see this information anywhere else so I thought I'd share, hope it helps.