I still think it is a bit questionable to have a character based on such an extreme edge case. One wonders, why was your troll and no other taken alive and trained instead of simply killed, incarcerated or exiled?
I am not telling you not to do this, but do consider these questions before you begin.
You could reverse the story and have your troll guard a Pandaren prisoner who teaches him the error of his ways in order to escape. Still seems a bit improbable, but I think it makes more sense than the Pandaren teaching a prisoner how to escape.
Thats just my quick idea though, it might have lots of plotholes.
That makes more sense. The troll is convinced to go renegade and seek out the temple by his captive.
It also presents an explanation for why they’d trust him enough to teach him. They’d have the former captive to vouch for him, and tell them how he turned away from his peers to come there.
It’s still improbable, everything has to go exactly right, but it’s better.
A quick post: The idea of them teaching the enemy to make them understand is not as far-fetched as you think. They wrote a short-story about how the Order of the Cloud Serpents found a Dragonmaw Rider and taught him the ways of the Order: compassion to master dragons etc to make him understand subjugation wasn’t the only route.