Here is my take (which is already supported by a lot of excellent observations in this thread):
WR was not the top priority. Pass rush was. WR might have gone as late as the 3rd round in the draft if Seattle found a DT and DE they liked enough in round 1 and 2.
That said, I've written for a while now that the prototypical John Schneider WR is a guy with quickness, speed, and YAC ability, with Golden Tate being the best example. Who is the undisputed quickest, best YAC WR in the NFL? Percy Harvin. Who spurned USC when Pete called him the best player in America? Percy Harvin.
I think ever since it became clear that Harvin would be traded the Seahawks have built their entire offseason around acquiring him. The term "mancrush" is probably an undersell. Not only that, but Harvin's skillset fit perfectly with Seattle's needs. They needed an upgrade in the slot, they needed more speed on offense, they needed a successor to Leon Washington, and they are always looking to add more weapons in the running game.
So no, WR was not the top priority- until Harvin became available and HARVIN, not the position he plays at, became the new top priority.