How do you get to Mar'gok in Highmaul?

I’m working on completing older content and would like to take down Mar’gok in Highmaul, but can’t figure how to get to him. Do I have to kill all 3 of the optional bosses? If so, they’ve all gone down pretty easy except the butcher, who I can’t seem to solo (Mythic). Is there any way to avoid Cleave/Gushing Wounds? I’ve tried going after him about 5 times now and gushing wounds kills me every time.

Did you try walking through the giant portal.