How do I progress beyond malice difficulty?

I thought the first 2 difficulties would be a cakewalk after coming to this game from vermintide 2 but I’ve found myself at a wall with this difficulty. currently I’m playing as a veteran at level 18 and most missions I do at this difficulty usually have people getting picked off due to some members rushing ahead and not being there for support or just separating during hard fights so everyone is isolated. Is there anything I can do to start winning these missions more reliably?