With offensive and defensive lines, you get what you pay for. It's a lot harder to game the system at those areas than it is at say WR or RB.
FWIW, there were reports after the past couple drafts that Seattle had their eye on a couple of OL making it to their 2nd round pick, but didn't get him. Fan speculation is that those players were Kyle Long and Mitch Morse. So I do think OL has been an early round priority, but the team has either been without a 1st round pick, or needed to trade down to accumulate extras.
I am fairly confident Seattle will draft a tackle at #26. This is a deep 1st round for tackles and Seattle will start the day with 9 picks, so they won't feel pressured to move down with their first pick. Seattle has four picks in the first three rounds, and I would guess that tackle, center, and speedy LB will be among them (unless Irvin returns).
All that said, I respect Tom Cable, but his track record with drafting OL has been pretty bad in Seattle. Carp, Moffitt, Sweezy, Seymour, Fat Rabbit, Bowie, Britt, Scott, Poole, Glowinsky, Sokoli. It's starting to feel like the same song and dance every year, with the same results every time.
After Okung left the game with an injury, Seattle's OL was playing three UDFA's (Bailey, Lewis, and Gilliam). It's nothing against those guys, but it illustrates how so many players were drafted and brought in here, only to fail to grasp their opportunity. The Seahawks have given Cable five drafts to develop guys, and with a few minor exceptions, it just hasn't worked out.
That said, Cable has done well with inherited players and veterans such as Okung, Unger, and Giacomini. I think it's pretty unfair to Cable that Seattle has forced him to build through the draft almost 100%. If they allowed him to pick a solid veteran here or there in free agency, it might go a long way.
Long story short, I'd like to see Seattle invest in their OL in both free agency and the draft. The current center, LG, and RT are all backup caliber players, and the two remaining starters are both free agents. I don't think OL is as big an issue as some do because I think spread + Rawls can cover up the smell, but I'd fully support a pricey overhaul to the OL this offseason. Trying to get by on the cheap just isn't working.