Maybe I am in the minority, but I am totally fine with a Okung-Bailey-Lewis-Sweezy-Britt starting OL for next season. The team needs to add depth and competition level players at a few spots, but that can be done with mid-to-late round picks. If Seattle drafted an OL at #63, I would consider it to be almost a luxury pick since the difference between that pick and Bailey/Lewis would probably be small.
I think the biggest need is WR, specifically a guy who can convert Wilson's deep throws into huge plays. Wilson is a very good QB, I have no issue calling him elite, but he generates a huge amount of his value from the deep ball, and right now our deep targets suck outside of Kearse and maybe Graham (I don't think we'll see Graham 60 yards downfield all that often). Wilson's YPA and QB rating dropped last season and the biggest reason was the lack of a viable deep threat.
I also feel that this need matches up very well with the talent that will be available in round 2 if Seattle is willing to move up. I normally don't expect much of rookie WRs, but if Seattle got Devin Smith somehow, I think he'd have an immediate impact and generate 5-7 TDs and a very high yards per target in year one. I think of all the players Seattle has a realistic shot at, Smith increases Seattle's point differential the most.
I also think that blocking TE is a big need, bigger than OL even, since we block with TE so often and our current TE group is full of terrible blockers. That's why I am not so happy about being penny-wise, pound foolish with Zach Miller. Of course, Miller is still available and if he remains available after the draft, there is a very good chance he'll be a Seahawk again.
We always need pass rushers, though it seems Seattle has identified free agency as a market inefficiency to supply the kinds of DL they like. Bennett, Avril, Branch, McDaniel, Williams, Hargrove, Brock, Clemons (trade) etc. Seattle has gotten fantastic value in FA at DL and I think they will work that pipeline as long as they can.
We need DB help, but it's such a poor class this year that it might be best to draft some project guys late and hope they turn into Byron Maxwells.