The whole "zero RB" concept is an outdated term, just like the "three down back". I could care less if my RB is a "three down back". If he's on a team that throws to RBs (KC/Det) on 1st and 2nd down, who cares if they play on third downs? FF is in large part built on statistics and probabilities, and as such people like to make sweeping generalizations like "3rd year WR" that are eventually revealed as outdated and no longer relevant.
All "zero RB" means to me is that you are willing to forgo the premium to secure a "3 down back" (pffft). The whole premise behind the strategy is that stud WRs are much more difficult to find via FA or WW whereas RBs are basically plug and play as long as the offense is right. (Deangelo williams, spencer ware, etc...)
I think you're oversimplifying a bit. I agree with your premise about a "3-down back" in the context you're stating, however I do not believe that is the generally understood definition of the term.
The true "3-down back" or more accurately described "workhorse back" is more typically defined as what used to be called a "feature back" - e.g. the offense "featured" the running back position, to the point that the offense moved through the RB. The order of the day was ball control + defense, and the running back was the premium position on the field, thus the premium position sought after in FFB communities.
Due to the evolution of the NFL towards a passing game (which rules changes have had a lot to do with) and the evolution of the OC's who game-plan more towards a short and intermediate passing game, using dump-offs and screens (like the DET offense you describe) the landscape of FFB has changed as well. Where in the past you'd have as many as 20 "feature backs" in the NFL, with better (LT2, Terrell Davis, Sean Alexander, Tiki Barber, Priest Holmes/Larry Johnson, Jamaal Lewis, etc, etc, etc ) and worse (Fragile Fred Taylor, etc) options, nowdays you have maybe 3-4 teams that truly "feature" a RB.
That, in my opinion, makes these true rare feature backs far more valuable than any RBBC back. Picking the right one can still provide you with a tremendous advantage at the RB position when playing against a team that's light on RBs.
Your example of Ware & DeAnkelo Williams is off-base - neither were plucked off waivers this year, both were mid-round draft picks in every mock and league I drafted in, with both going a full round ahead of ADP in both of my $ leagues because their roles were known well before the season started. Better examples may be Theo Riddick (who I drafted in the 10th round as my RB4) and Coleman, who went in the 12th.
That said, it's still not a great example, since both those players were drafted in most every league - and with more and more fantasy managers targeting their own handcuffs as well as the backups on just about every team, and with more and more people buying in to the "ZRB" strategy, I would suggest that the FFB landscape has changed to the point that it's getting much much harder to just pluck up a "plug and play" RB during the season.
Looking at the FA list and rosters in both of my $ leagues, every RB worth rostering is rostered. Every backup is rostered. And several speculative RBs are also rostered. If anyone goes down with injury, there will be no one to pick up in either of those leagues.
So while I respect your opinions, I disagree with your poo poo-ing the feature back - in my humble opinion, it remains the single most valuable position. David Johnson owners have a huge advantage in any format this year, but especially in PPR. I was pretty psyched to get him 1.04 in one league and super pissed when in my other league I landed 1.03 and it went DJohnson -> A.Brown -> me. Julio Jones is a nice fall-back, but in my opinion the dropoff from those two was significant. I almost took Lamar Miller there, and in hindsight wish that I had.
