The 4.4 kernel relies on the device tree more extensively, but that should not really affect the current installer.
I guess the more likely issue is that the soldering on the pHAT DAC is flawed in some way. Did you solder the included header or used a custom solution?
Did you solder all points? You can see the important ones in the pic linked in the following thread:
http://forums.pimoroni.com/t/phat-header-soldering-the-lazy-way/1690
… I might be worth giving those a touch up and see if things work then.