dude you're clueless.
I hate skrillex as much as the next guy, but he doesn't even pretend to 'mix' live.
Here's why you're wrong:
First, the dude uses a fucking MPD. you can't mix with an mpd. you can trigger clips, samples, and effects, but you can't mix with one.
Two, when a celebrity or someone who doesn't actually know how to DJ 'DJs' the person who actually does the work for them would be either off to the side of the booth or backstage, not in the light/sound booth. Theres no reason or need to risk being caught in the act by doing it in the open.
Three, why the fuck would somebody need three people to blend from one song to another? most software can basically automate the process, even if somebody was doing the work for him, two extra people would be completely unnecessary.