I think we need to define what we're talking about. By definition, Ted Ginn Jr. could be classified as a deep threat. Same with Darrius Heyward-Bey. Neither of them are worth throwing to. But the OP is talking about the classic #1 outside WR, the freakish big WR justifying $10M+. No Torrey Smith, no Sanders.
As for Thomas, as I mentioned, he hasn't been utilized that way. Brandon LaFell averaged more yards per catch (13.9) than Thomas this year (12.4), who was just a bit ahead of Edelman (11.3). A huge part of that is the QB obviously, but the point is that the team succeeded based on other factors, not a huge #1 outside deep threat, but by utilizing him as a possession receiver.
The OP mentions the following (not Torrey Smith, not Sanders):
There are a few HOFers in that group, and potential HOFers as well. Of course not even half of them even made the playoffs, with only one making it to the final 4. It's not a prerequisite as the OP claims. Plenty of teams do fine without that freak.
Also, just because he's not classified as a WR, people overlook the fact that we do have a freak. His name is Rob Gronkowski. He averaged over 16 yards a catch, more than big-play explosive receivers like Green and Jones. He's a TD machine as well, and virtually uncoverable in the redzone.
I just don't see why people keep wanting to drop $10M on an outside guy we won't utilize much. Everyone points to Megatron...yes, let's follow the Lions. Or the Falcons. I want to emulate that franchise.