You do take one attack for them, it works as intended. I Intervene when I am above 90%, he just took a hit and his taunt is coming off CD in the next few seconds. I intervene, steal aggro usually, OT taunts back, I eat the hit and boss is back on him. Gives him an extra 3-4 seconds to get healed up. This works 100% and does not seem to be affected by Baleroc's offhand.