Tua isn't bottom tier, nor is Dalton. Nor Rodgers, though maybe he's approaching it.
The fact is, only about 1/3 of the QBs in the league are top tier. Most teams face groups like that, a third top tier and two-thirds who aren't. There are exceptions, especially in divisions with a great QB group, but this is how it looks, on average.
Dunno. But everyone should.
There is no one stat, beyond wins and losses, of course, that tells the story perfectly. But when it comes to isolating the performance of an offensive or defensive unit, season yards may be the best one.
Of course, you have to look at all the stats, at the whole story. But total yards is absolutely a key stat.