Hello,
a guy took me as Mentee and then powerleveled me. He had 2 Wynn Summoners. Used Shadows with which he attacked the RBs. The Wynns stood as far away as possible from RBs. I did some dmg as well. He leveled his own Healer and did some healing / damage. This way he easily killed RBs from lvl 55 to 80 and pushed me from 50 to 85 in some hours.
How does this work? I attacked a low Lvl RB with my Wynn's Shadow. The shadow got the raid curse immediately.