I know that no one has posted on this in quite a while, but I want to expand on this theory...
I agree with Munin - Jezrien is evil, or at least misguided... I don't think that he's the face that Kal sees in the storms though.
From the Prologue we know he's broken - but still regal
He then starts espousing something that, at the very least, would make Syl uncomfortable:
This sounds eerily similar to Taravangian:
Even some of the descriptions of bearing are similar between the two:
I think that Taravangian is Jezrien. I don't know if he's working for Odium or trying to make up for the poor decision to end the Oathpact. I think he's lost his way and is no longer the man that became a Herald.