Um... no, a lemon is not mediocrity. Newhouse was an average NFL player, that's not a lemon. You can get away with 2 of those guys on your OL, but if all you have is mediocrity across the board you're going to have an offense that can be easily exploited by a good pass rush, or one that is unable to run against many teams. in 2011 they had Sitton, Wells, Lang and Bulaga on the line - Newhouse was the least of the group. In 2012 it was the same group except Wells left and they signed a washed up Jeff Saturday. They went from 15-1 to 11-5... coincidence perhaps, but losing good OL hurts an offense.He played like a lemon for the Packers. Your stats pretty much demonstrate what I'm saying about O Line quality not being very important, and mediocrity being good enough.
Right now, Myers is basically mediocrity at C, Rhyan could be a liability. Tom and Jenkins are pretty good and Walker is improving. Nothing wrong with trying to get a LOT better at OL.
Moreover, who are you playing if Myers sprains his MCL? What if Tom hurts his shoulder? They have NO depth. Drafting a guy in R6 who is a year or two from seeing the field is not an option unless you want to get Jordan Love killed.