Heh, you know, I figured, what the hell, and plugged my uDac2 without a powered hub into my Moto X a few minutes ago. Ended up working like a charm! So I do hope this is in fact just a Samsung design flaw. But people should still be careful, in general, not to try DACs that have a power hungry reputation on anything irreplaceable.
The FiiO E18 portable DAC/Amp doesn't draw much current and never hurt my S3, Note 3 or iPod Touch 5G.
When it comes to the GS3, it's Caveat Emptor