I think it ended up being 4 ongoings which completely crippled Iron Legacy and I think we beat him in two rounds.
Yeah we were playing with main priority to remove as many ongoing cards too. The hardest part to us was more the first damage he takes each turn gets redirected. So we tried getting as many start with 1 damage cards per person like Tempest and Omnitron-X , still it felt crazy. We'll look into nightmist thanks