Seemed to be yes, now you know better.

Seriously though, BS said in a book tour that: "The black/dark aura around Rand is partially, but not entirely, an effect of True Power usage".

Partially, but not entirely. It seems pretty obvious now in hindsight that the whole dark aura in the last book was likely meant to show that Rand has some kind of power to affect the world somehow in fullfillment of the dragon&land-prophecy, whether some unique dragon-power or a manifestation of uber!ta'veren. The fact that he had used TP caused this power to go corrupt however. There were other clues such as ta'veren only causing bad things, etc. We also know that the dark!aura directly caused things to spoil and rot.

And this was unique to Rand. None of the other forsaken have such auras despite the fact that they have touched the TP a lot more. Ishamael was the only one that had anything like it, and he was super-TP addict and even then the effect did not look entirely identical (and did not affect the land). This has caused a lot of speculation, but it does suggest, even before ToM, that the TP was not the only reason the aura happened, implying it had something specific to do with Rand/Dragon too.

So yes, there was foreshadowing and this did not come entirely from nowhere. Infact its likely that the dark!aura was written strictly so that we could see the light!aura and be prepared for it.

It is true that this is the first time we have actually _seen_ the light!aura in the books, but really, so what? Everything has to appear on the scene for the first time sometime. It just happened that the light!aura only appeared now that Rand has finally accepted LTT and found peace. I think it was a perfectly fitting time to show it.

As for what exactly it is, what causes it and so on, I expect the book will hopefully reveal something more to us about this. Though I suppose if Rand has only a few chapters, we might have to wait until the final book (grr).