A reach is all relative. You have to find players that fit your system and these were players the Raiders felt fit their system very well. They have a clear outline of the type of player they want and make their draft board accordingly. It's no different from what the Patriots do.
Except the Raiders have a system that is perpetually broken and rarely wins. The Raiders suck, their system sucks, their owner sucks and their fans might suck for not mobbing Al Davis' vehicle as he tries to leave the stadium and giving him some mob justice. Let me ask you, if one of your first two picks every year are DBs why aren't they sticking around?
Merely having a system doesn't make their choices any more logical or good. A person using the Martingale System doesn't make one a better gambler.