Sorry I'm a bit late to this but I have just been playing with various connectors, adapters, hubs etc with a tablet so I thought I would have a go with my Moto G after reading this.
I presume you ( swab ) are updated to the update to 4.4.2 ! ( Originally the Moto G worked with OTG attached drives but this was lost with the original 4.4.2 update. However, that has now been more or less sorted by a further update ).
I had confirmed that this new update was working but had not tried with a hub. I have a micro USB OTG Y adapter which allows further power to be supplied, but the first thing to realise is that this does not power the phone - it only powers the hub and items attached to the hub. I can confirm this is the case with a couple of hubs I tried with dac and drive attached. I played some tracks through the dac from the phone OK, but the drive was NOT recognised on the hub ( although it is recognised and can be accessed when attached directly to the OTG adapter ). So, it looks as though Motorola/Google have only partially solved the problem. ( My Samsung Note 8 can access the drive and dac and a mouse/keyboard all attached to the hub at the same time although the hub does need to be powered ). So this agrees with your findings with your hub experiments and it is unlikely to work unless there are further relevant updates.
It would seem that your best bet is some kind of wireless access to external files such as that suggested by Theogenes, above, and plug your phone directly into the dac via OTG.