I haven't seen a lot of Dragic, but from what I have seen and read, I'm quite excited about his potential. That said, I think it naive to think he can be the number one back-up for Nash.
If Steve remains healthy, then Dragic playing 10-15 minutes a game may be fine. But my understanding was that they wanted to substantially cut down Nash's minutes and even sit him a few times a year. If the Suns are to be a championship team, they need someone capable of holding the fort if Nash gets hurt or they sit him a few games.
I'm not convinced a combination of Dragic, Barbosa, Strawberry and Hill at the point is a recipe to a top 4 finish in the West, and we saw this year that not finishing in the top 4 leaves steep hill to climb to get to the finals. I hope Kerr has something up his sleeve.