Strictly speaking, the Macbook is under no obligation to provide more than 100 mA to a device that doesn't properly negotiate for it, which I don't get the sense the power dock has the capability to do.
In practice it does seem though that it can work with a good 5v-3.3v regulator on many computers . I will say that my personal experience with doing so is using a well designed switching regulator, which converts energy unlike a simple linear regulator - ie, the computer has to supply somewhat less current at 5v than the device is drawing at 3.3v.
Ultimately, power issues are the #1 cause of reboots (especially around the time of wifi startup) and all of ultimate power source, regulator, and cabling should be considered... I had a system I was ready to give up on, tried a different (and confusingly, much smaller physically) source and regulator, and it's been wonderfully stable since.
Looks like your connection to Community was lost, please wait while we try to reconnect.