To a degree, I agree with the OP. The importance of someone like Verreen, is for specific defenses. Look at the last superbowl for example. Vereen's contributions I would say were almost as important as Edelmans (or Amendola's or Gronks, etc), as he kept drives alive, and allowed the Pats to score TD's in the 4th quarter. Being the running back that catches passes well, and gets YAC, was huge. Missing that element is a significant loss, especially when playing top defenses like Seattles (or either NY teams or even Buffalo).
Also, I think the injury to Faulk in 2007 was probably one of the biggest pieces missing for Brady when playing against the Giants D. He barely scored despite having perhaps the 2 best receivers in the game su(Moss, and Welker). Who knows what would have happened if Faulk was playing, but I suspect that it probably would have changed some of the offensive drives that game.
Now if the question is whether loosing Lewis or Edeman is the greater loss, I guess it comes down to depth, in that Amedola is better than White, and that is why perhaps loosing Lewis is a bigger issue.