I was initially thinking that norm-Corax had been opposed to psykers at Nikaea, but couldn't find any reference to the event in the only Nikaea article I could find in IA: Thouasnd Sons.
Other than that...Corax was one of the marines most opposed to the integration of psykers (according to Lexicanum, anyway).
Other than the lexicanum, which I would not take at face value, do you, Octavulg, or anyone else, know a proper canon reference for this?
I want to have Corax at Nikaea - the place where the Tsons get grabbed away from Tzeentch's clutches and so where Corax starts getting his vulture dreams - but if he is there he may as well do something. Considering what happens later it would be appropriate that he opposed psykers, only for the Clonelord to boost the legion's psychic potential behind his back... It would be a good reason for Corax to confront Bile about what exactly he is doing, and thus force his capture.
Plan for the next few days - review the article and make a series of small changes, then work on firming up the earlier sections. I doubt that I will get anywhere near finishing by the end of the weekend, but if I can make as good progress as I did last weekend, then I will be happy.