I don't know if I'd say that anyone who doesn't have an injury excuse actually looks worse, even if they don't necessarily look better. I would have added CCJ as 'Better' prior to Copa America burnout.
Yearwood and Clark are the only guys on that list marked 'worse' that I think have any real potential to get better, and I agree with McSoccer that Clark's surgery took a toll. Tarek is older and has always been error-prone, Omir and Egbo are not MLS-quality players imo.
I think Struber's done enough on the development front, fact is that the team is so young he's being asked to be both a reserve and first team coach at the same time.