Well, you've got a point

Nash and D'Antoni needs each other to be great. Before nash became a sun, he was good but far from MVP. A little bit like MJ and PJ, MJ was scoring champ but never an MVP before PJ took the coaching seat.

Your case of Mav became a better team after Nash gone remained to be seen. Don't u remember Nash led sun sent the Mav home last season? With the big 3 including Nash, (not as good as now), mavs went to WCF, the current Mav has yet to pass the second round. So, case closed here :)