On the case of Wagner I think its good to have a great pass protecting RT, I don't think he's a mediocre run blocker either. While he's not the nastiest guy out there nor is he the best he does maintain his blocks time-to-time, I do see your point, if we're overpaying for an OL give me Zietler over Wagner in a heartbeat, but I'm afraid Zietler is the far more likely candidate for a monster payday than Wagner.
In Williams case I can see the Ravens desperation to keep him. Timmy Jernigan and Lawrence Guy were dreadful during the final stretch, I think Jernigan went four games straight without recording a single stat. Guy on the other hand got caught over-pursuing on runs, missing gaps, and got taken out of plays time to time. If those two carry there play from that stretch onto next season and no one steps up and you lose BW, then the run D might be in big trouble. Still don't think its worth it because I'd rather just try my best to find a replacement but I could see the Ravens case for pushing hard to keep both.
I look at it from a value standpoint honestly. What's the value of paying Wagner 10M+? Not that great if that RT isn't a game-changer like a LT or even LG can be. I honestly can see the value in someone who can stuff the run, but in 40% of plays that he's not on the field, it can honestly hurt a team. With that said, if it were such a big problem, then I don't think the Ravens would be that interested in bringing BW back. There may not be value in stuffing NT, but there is certainly value in being able to stop 1st and 2nd run plays.
I think we're going to be really surprised. Either Wagner and Williams get a monster payday, or maybe they don't and return here.