Teoscar - 102 wRC+
Gurriel - 135 wRC+
Varsho - 97 wRC+
Kiermaier - 131 wRC+
There's a slight downgrade there while they went from a below average defense to elite and they added one of their best relievers. They also added Belt.
They've scored 317 runs this year. Through the same number of games last year, they had scored 323. That doesn't seem particularly significant to me.
This.
Roster moves haven't shortened the lineup, it's been underperformance from Springer (to start the year), Chapman (after April), Kirk (though he's still ok, just not great like he was last season), and Vladdy (though "bad" Vladdy is still in the top half of qualified 1Bs by fWAR and top 10 by wRC+. So "bad" Vladdy is still better than quite a few first basemen in the league).
Chances are not everyone's going to dig their way completely out of their respective holes, but it only takes a couple before things start looking a lot better.
Gurriel's going to regress a bit because he always does, though it will be countered by the juice he gets from playing in Arizona.
though on the other hand Keirmaier is likely to regress some too. He's never been this kind of offensive performer in his entire career and it's hard to imagine that he suddenly started hitting for massive amounts of contact just this year. Guys can get the Bautista late-career power surge but rarely do they get a late-career batting average surge.