I've been farming Seigebreaker inferno with a partner and I've found that if you have Furious Charge and you target the backhalf of his body you can charge through him but not all the way. You will charge inside of the boss and he won't be able to hit you with his frontal melee attacks as they will simply go over you and stay in place allowing you to freely DPS him. However, he can still grab you out of him.