No not really. These three guys came in at a perfect time. They have a lot of buzz around them now and it is a perfect grouping. Who else would have fitted into the Shield at that time? Roman was still being repackaged at that time, Kruger was also being repackaged. Rollins had just become NXT champ and Wyatt had just gotten injured. And with NXT being just off the ground back then as weird as it sounds they needed to keep some of the top developmental guys there to establish it so that people would come watch before calling them up. It's a smart and low risk test to see if a guy like Seth or Dean draws.
Ambrose, Rollins and Reigns has some great momentum going now and are doing wonderfully. Shield doesn't need to be the size of Nexus. The more guys you bring up at the same time the larger the risk that you drop the ball on one or more of them. A 3 man group is easier to handle. Cena, Randy and Batista debued at roughly the same time and since they only debued those three they could focus on and build all three of them into big names.
No need to rush guys up to main roster. Guys like Ohno, Wyatt and Big E will make big impacts in their own time.