I agree with your statement that most players come into college with the ability to pass and play defensively.
Mira Topic, Alyson Jennings, Ashley Engle, Heather Kisner, Cat McCoy, and now Sydney Petersen are a few names that I think came in ready to play at the collegiate level (since Jerritt's tenure).
Kiley Hall, Sydney Yogi, Sarah Palmer, Sha'Dare McNeil, Kat Brooks, and Amy Neal are the ones that had the ability but REALLY had to develop and refine those abilities to play at a high level.
If the coaches are not able to develop the passing/ball control/floor defense that's needed to be a consistent Championship-caliber team, then they need to focus on getting players that already have those skills and offer them a scholarship, instead of hoping that these walk-on DS's will develop.
WIth 12 scholarships, I think 2 need to be given to Libero/DS players; 1 definitely for a libero and maybe offer a 2-year deal to a DS player that comes in as a walk-on and if she is the first DS to come off the bench by her JR year, then she earns the other scholarship. I mean, I would gladly trade-in Orie's scholarship for a DS that could actually be a consistent force in the back row.
I think there is a large pool of 5'8-5'10 High school OHs in Texas with great ball control skills that could transition nicely to a DS role if they were at least offered a 2-year scholarship at Texas.