Good thoughts. I always find it interesting that the term "positional scarcity" is used incessantly in fantasy baseball, yet almost never used in football talk...
I agree that WRs are often neglected, and I certainly agree that picking a WR in round 1 can be a viable strategy. One factor which you have to add to your analysis, however, is consistency. If a WR and an RB both average 15 points a game, for example, the RB is likely to put up a number fairly close to 15 in any given week, while th WR might give you 25, but might also wind up with just 5. When picking RBs early, you're also paying for consistency.
(We have an article in the works, by the way, that focuses on when to start WRs and when to use RBs, which touches on just this issue - stay tuned
How did you calculate dropoff? Did you consider TE in your analysis? I'd certainly be interested in seeing your results.