In terms of the 10/12 channel, like others have said, I think Foley will go to a wing, with AAC (Adam Ashley-Cooper) defending at 12 and Giteau at 10. I imagine they would then be relying on Hooper to protect the 10 channel from having to make too many one on one tackles with his shooting defense, and Pocock lurking behind to clean up any he misses/make some pilfers.
As for the general issue with hiding two sub par defenders, the Tahs have been doing it with Beale and Foley (and Giteau is a better defender than Beale). I know it's Test level and it's different, but at least we're not going in completely blind.
Foley's misses by the Argies were not "normal" for him, the ones I noticed were all him being stepped around while going for a "around the legs" tackle.
He bends his back, puts his body on the line and has a go