Why are you going off of last season to describe the raiders offense? It is a completely different situation now. A brand new head coach, o-coordinator, and o-lineman coach. They completely restructured the o-line, and brought in 2 new starters. The biggest difference is o-line coach tom cable has introduced the zone blocking scheme similar to what the broncos and falcons use. If you've watched the preseason games they are blocking much better then last season and giving the qb time which was their biggest problem last season. If they don't get the o-line improved they will have problems again but so far it is looking a lot better.
And in regards to the offensive weapons, the vikings have a group of inexperienced no name recievers, I think their top wr is bobby wade. A young inexperienced qb. Adrian Peterson will be good though. The raiders now have 2 veteran qb's culpepper and mccown, which I think culpepper will get the starting job. They are solid at rb with jordan and rhodes. And wr porter and curry are both good, also rookie zach miller will is already looking good this preseason.
I do agree with you the vikings have a good defense, but the offense won't be on field enough to help them out.