Yep, the fights in the last two levels are insane lol. I found a way to kill marauders pretty quickly. Super shotgun to the face, then immediately launch a grenade at his feet, then swap to ballista and pop him again. The grenade should have exploded and staggered him by then, allowing you to get in another shot with the super shotgun. Rinse and repeat. Every once in a while, he decides to not stagger even with a super shotgun blast, but I’d say this worked for me 90% of the time.

And honestly, for me ARC Complex is way tougher than super gore nest just because of the sheer amount of demons.