The focus of live mixing for major shows turned from focusing on single channels to the master channel. Sure, you have to be a mixing engineer during the preproduction stages, and you might still go back and tweak some channels on various cues and snapshots during setup, but when show time comes, you are zeroed in on the master bus, mostly taking care of snapshots being fired at proper moments. From a studio point of view, you are not a mixing engineer anymore, you are tweaking the summed results of a mix - you are now a live mastering engineer.