For successful minor league development into the majors? One legit starter in addition to Ober and Ryan (if one of them takes a step back, that's bad), and 2 that might be? Plus, at least one legit starting hitter. And, a bullpen made up of younger guys that is around median. So, sure, 4 legit starters from the system works for me.*
*if they deal minor league guys for a proven MLB player, the ratios clearly change