Agree completely with your assessment but as important as a DL is, no team is going anywhere without a solid OL, or a solid WR unit or a very capable secondary or even good depth at RB.
Raiders have a lot of holes all over this roster and think Spy could go in almost any direction with BPA in the second round and still hit a need that must be addressed if this team is going to have future success.
He ain't going to address all the needs in one offseason. Like you I prefer to build from the trenches out, but that said if there is a run on those positions, I have no problem with Spy going BPA and picking a player that fills another need on the roster.
I have come to terms with the fact that this is at least a two year process under Kubiak's direction to get this thing where it will really work.