Well, since we're tossing around the idea of Dez coming back, I still hold the same opinion. If his skills have declined to where we can't expect him to make that play, he shouldn't be brought in.
Here's the problem with your position, until he's actually playing against competition, he 'can't win', can he? Running routes against air or some wannabe football players doesn't allow him to prove anything either way, does it?
Neither you nor I can tell anything about 'declining skills' or not one way or another at this point. But if you bring him in on the 90-man roster and see what he has (or doesn't have), you can then make an informed decision. That's all I'm advocating, making an informed decision. After that, let the chips fall where they may.