I personally like the idea of the Taln in WoR being actually Jezrien, that would probably also explain why Hoid ran off while accompanying the carriage. There's after all no point accompanying/guarding not the real thing. Also the best way to replace a mad herald and not get caught is to replace him with another mad herald.
Also as a side note/theory which I personally do not believe to be true but which was never considered here IMO is that Tanavast(Honor) may not be quite as dead as we think him to be. He may be dead as god/shard but kind of alive as a person. After all the madman knows stuff which is probably only known to the following persons:
Tanavast/Honor
Reya?/Cultivation
Raise/Odium
Hoid
Heralds