I doubt Peerless was double covered much during his Atlanta stay. I could be wrong, I suppose. He never drew double coverage in Buffalo, or least not very often.
I think Evans has one hole in his game, really. He doesn't come back hard enough when the QB is in trouble.
But other than that, the fall-off in production is due primarily to Fitz not going long often, and not being particularly accurate. He had been more comfortable with the mid-range routes, and the Bills have not used Evans in that role much. You might have noticed in one game this year, Stevie left the game (I think it was Stevie) and the Bills started to use Lee over the middle and on some shorter routes. I believe he caught every pass thrown in his direction.
I would expect, as Fitz becomes more and more confident, Lee will become a target more often. But even if he doesn't, Fitz will find his other WRs harder to connect with if there is no deep threat. And right now there isn't one on the Bills.
The idea that Lee doesn't get open, doesn't run good routes, is preposterous. He is open enough, on nearly every play, if the ball is thrown to the proper spot. Remember the mooks that claimed Roscoe couldn't run routes, based on his lack of production under Jauron? That was all BS, too.