Yep the 10/12 combo hasn't been great, and there's a definite case for having a solid, experienced player like Carter at 12. As well could consider Horne at 12 Tahu at 13, who you'd think would be better there attacking-wise, and he'd be good at bursting on to flat cutout passes from Beale. Tahu being a leaguey is obviously used to attacking with a few less defenders around which he would get at 13.
Horne though, the type of player Wallaby and Waratah supporters dream about coming through the ranks, is good in both positions, and maybe better defensively at 13 than Tahu.
I'd probably continue with Tahu for a few matches, and swap him around a bit at 12 and 13, and see what happened. Let Hickey prove his worth as a backline coach and get him playing well, same as Mick Foley's doing with the forwards!