Definitely a huge upgrade. Williams is a good back and Blue is electric. The combination of those two are better than Dowdle, though I agree Dowdle was underutilized and play calling was abysmal last year for the run game. More importantly, Martin was very hurt and not himself last year, so I think with Beebe in his second year, Smith and Booker at Guard, and Guyton in his second year, the OL will be much better in the run game. Perhaps most importantly, we finally have a real WR threat outside of Lamb in Pickens, Schoonmaker came on last year as a passing threat, and Ferg should be healthy. This means teams can't just stack the box against us and dare us to run. I think it's been undersold how much both the passing AND running game needed that additional threat at WR.
If everyone is healthy, playcalling is decent to good, and the OL gels, this team should be right back in the mix if Dak can step up and play up to his contract. If he can't then it's time to go.