I'm not thrilled with Gray as an only addition to the rotation.
I do think I disagree with your take on the rest of the rotation. I would prefer more quality than quantity, but decent/promising quantity is not a bad thing. I think we have Crochet, Bello and Gray who are solid SP'er expected to start 28-33 games and go 160+ IP.
We should be able to fill the 4 & 5 slots with a couple decent pitchers. Sure, we can scour the recent trends, injury reports and selected sample sizes of poor pitching, but we all know projecting what we'll get from these guys is near impossible. I'm worried that we may have to go through 6-7 pitchers to finally find the two that do well enough, and by then, we've lost 10-15 more games than we might have had we found the right two in the first week of the season.
I can find very nice stretches in the careers of Sandoval, Crawford, Dobbins and Criswell. Some, like Criswell and Dobbins are their most recent starts. Sandy & Crawfish were from more distant pasts. Then, we have 3-4 promising young guys like Harrison, Early, Tolle and Perales. That's 8 guys for 2 slots.
No doubt, I'd love to have another solid SP'er, but I think we are running with what we have, now. Of course, if we trade Crawford and Harrison in a package for a bat (maybe with Duran and or Campbell,) then maybe we have another SP deal in mind- like Alcantara, Gore or M Keller. I doubt we'll see Ryan or Lodolo or better.
Get us KMarte and Alonso and I can live with Sonny Gray and nobody else.