It's a little early to say the Raiders are setting up Shell to fail. They were in awful cap shape an weren't/aren't in a position to throw around big money. Most of the money they have allocated for free agents should be used on defense, which has problems all over the place.
Besides, I don't think they need an impact QB to run that offense. With a decent QB(Brooks, Griese, & Collins are still out there) and a healthy Randy Moss, the offense should be good, maybe even great. I'd rather have Brooks than Collins or Griese, simply because he is infinitely more mobile than those statues.
The draft? I'd love to have Vince Young, but, again, defense is the more pressing need.
If the Raiders leave the draft and enter camp with Tuiasosopo and Walter competing for the gig, then I would agree that they are setting up Shell to fail.