Here is a link to Throne of Heroes thread.
http://forum.shrapnelgames.com/showthread.php?t=40540
This is NOT a new mod. It is an update to Worthy Heroes 1.8 Middle Era only.
It does add new heroes. The readme includes the changes that were made. Human heroes which are generally underpowered and useless after the start of the game, receive new abilities tthat inflict afflictions. Four or five heroes got a new modding ability, onebattlespell.
Turin the Mod author, the guy who created Worthy Heroes, helped edit it and gave it his stamp of approval. It was not called WH 1.9 to avoid confusion with a planned future update that includes all 3 eras.
Throne of Heroes is an update to Worthy Heroes 1.8 Middle Era only. It makes no changes at all to the EA or LE WH 1.8.