Under-rated?
Ahem. Er, no.
If anything, they are over-rated. Yes, they are better at pass blocking than at run blocking (though it wouldn't take a whole lot). But were it not for Rodgers' and his running/scrambling ability, they'd have double the sacks they've actually given up. So, IMO, even just looking at their pass blocking, they still are mired in the average/serviceable category.
(This opinion of mine, of course, surprises no one.)
IMO, Ted is really good at almost everything he does. But I think the Packers ability to scout/choose OL is probably his (and the scouting department's, generally) is his biggest weakness.
And do not be conformed to this world, but be transformed by the renewing of your mind, that you may prove what is that good and acceptable and perfect will of God.
Romans 12:2 (NKJV)