Clearly our current FO believes strongly that you can acquire OL in FA. That's why it hasn't been a major perogative for them. They went with Walker and Dockery, and they knew that was their plan, to pay big bucks and bring someone in, so it only makes sense that they haven't invested as much into the O-Line in the draft (however as you pointed out since '06 they've approached the position 6 times which isn't a low number-- they're trying).
I think that the major need of the team is Center, and we'll see if they approach it similarly and look to pick one up in the off-season. Personally, after the Mike Williams tragedy, I'm all for only picking up proven linemen.