Just to be certain: you've completed the quest associated with the burning monastery, correct? If you haven't, then do so and I would think the Tyundii quest should trigger (slay the three demons to the north and then return to the monastery, and get a free champion). If you have, then I'd think that your campaign is broken in some way and would suggest uploading a save game or perhaps trying to reinstall the game.

Also, did you see a Shrill Lord spawn in, and get a message about some general who serves Karavox slaying it and giving you some soldiers? Because that should happen around the same point in the campaign, though I cannot recall at the moment if it's before or after you return to the monastery, though it should occur before you go to the shrine where the first piece is found. If it didn't spawn in, that would be an indication that something about the scripting broke, though you might be able to 'fix' it if you can get the Shrill Lord to spawn by running back up to the monastery area or the crossroads above it and moving around up there for a little while to try to trigger it.

The burning monastery quest line is a prerequisite to the Tyundii quest line. If you look at the quest log, you're told to go visit the monks at the monastery, and then you see that the place is in flames and you have to try to rescue them by recovering the key to the door, and then the lone survivor comes with you and you can start working on rebuilding Tyundii.