I picture an empowered Ret Aura more like a Legion Blessing of Might for everybody: upon activation the whole raid deals additional holy damage for 6/8/10/whatever seconds.
But I already see the outcry on the forums: paladin op!!
That's the general problem I have with returning auras: either they are negligible or they are absolutely required in every group/raid. Other classes will hate us even more. A problem I can see only being solved by giving other classes similar effects...shaman totems come to mind. But then people again will cry about "homogenization".
It's quite a tragic conflict: whatever blizz will do with auras, either paladins will hate them or the other classes will.