I keep thinking that McMillan closer to a TE than he is a WR. To use an NFL analogy, he's more Aaron Hernandez than Bubba Franks.
Right now, we're running a bunch of 3 WR sets, with Norrell and a WR (Gush usually) on one side, McMillan/Campbell on the other. If they run single high safety, he's gotta shade to the dual WR side, and that opens a power sweep short-side. If he doesn't shade, Norrell runs right by him and you get a big gain. It's a really simple game-plan, but thats part of why it's so effective.
The danger of running a cover-2 shell is if Maysonet gets past the first level, it's him vs a Safety. That's highlight material every time.