Basically what you do, is when he casts Headlong Charge and starts stampeding the room, you taunt him, and he will run almost twice as fast and he finishes his charge a few seconds earlier. Thats it. (Might be someone who didnt already have aggro on him that needs to taunt, not 100% sure, but taunt in general works)
What this does is to lower the damage the raid recieves during this phase, because since he finishes his charge earlier, the massive AoE ends earlier. We have been using this for quite a while on Mythic difficulty, and it makes life abit easier.