See, the problem I have with any sort of Fain corruption / SL corruption theory is the fact that we haven't seen any evidence of this happening ANYWHERE in the series so far.

I mean, if this was possible, don't you think it would have happened during all those month's Fain waited on Rand in Falme?

Or how about all the time he spent at the Fortress of the Light? No side-effects mentioned while he was there or after he left.

It seems his effect is pretty localized and sort of low intensity. The WC squad he was in charge of was simply described as dirty and unkempt, surly and unfriendly, etc... And he was with them and led them for months and months.

So, because of these reasons, I'm not buying into any 'Fain Effect' theory of any sort. RJ described Fain as a wildcard, and I think that's exactly what he'll be in the end.