George Lucas said in the commentary for TPM that in Ep. 4 the story was told through the eyes of the two droids. Those two doirds would have us meet Luke, who would introduce us to Obi-Wan, and so on. In TPM it is seen through the eyes of the two Jedi. The Jedi intoduce us to Jar Jar, who take us to Theed to meet the Queen, and so on. This just from what Lucas has said in various commentaries for the movies.

I think that if anyone could be called heralds in TPM it would be Qui-Gonn and Obi-Wan.