I have had Hustlers for some time now. Don't see the motors having many problems. Out of the 12 I have, I had only replaced one wheel motor on a Super Mini Z (over 2000hrs).
It maybe you have a bad batch but, the way I see it, it is your dealer's responsibility to pursue it with Hustler. He is selling it and should goto bat for you. I am sure if there is a problem with a batch of mowers, Hustler would know about it and resolve the problem.
Talk to your dealer and remind him how much business you gave him.