New to the forums - and wow, can I just say everyone, I'm so glad to have found these.
On to my take - In my opinion Taln at the gates is Taln in the camp. Which I think has been confirmed by WoB, but just to add my two cents. Upon his arrival the gates "the gates shook. Something pounded on them from outside...the gate shook again, as if something enormous were outside...all was chaos and confusion as the gate thumped yet a third time, powerful, shaking, vibrating as if hit with a boulder." He is later described by Shallan as having hulking arms, hands that could crush her like a cremling, and Amaram described him as enormous, built like a wall.
Anyway, the man described at the gates, strong enough to make the gates shake by simply pounding on them, matches the man who's physical strengths and speed are noted at the camp. What I think is interesting was folks thinking some how another Herald is in his place. Not sure they can even do that, but Jezeren was noted only for his beard and regal appearance in the prelude, and that he's drooling made by Nalan. Some think Kalak is the wounded bridgeman who spoke Alethi, (or has that been confirmed)- if he was indeed that wounded bridgeman why wouldn't he show those reflexes and hulking nature? Can't be Nalan. None of these men exhibit this strength and speed (though Lift noted that Nalan moved quicker than he should).
No, what I think is more likely, and as hit upon in the post above by EmTrevor, is much like the Hoed who were broken, and Brandon being coy about saying the person who claims to be Taln, and the fact that we see throughout the novel you can be called a Radiant, but not be one until ready - I wonder if Taln can't be Taln until he is unbroken? Perhaps like how the city of Elantris' power was restored?
Complete side note, but while in some chapter icons the images seem to align to a herald being present, there are others they are not. Like Interlude 8 - A form of Power - just has Eshonai present, yet there are pictures of Nalan I believe? Seems odd. Throws into question why we see Chach and Hoid on Interlude-7.