I think we need to model user behaviour as best we can. I see personas as a way to share those models and as you mention a way to enhance story telling and role-playing. Personas is certainly better way than a HTA to communicate user model to a group especially non-experience designer.

I also think like you the most important aspect, are not personas per se but having the right having user models or personas. You mention the feeding of the models or personas with frequent field study and I agree with you it is the key

The story you describe about field technician where war stories exchange were the biggest contributor in their education is the key finding. It comes from observation and field study. Personas or not, what is important are those insight. They are crucial for design decision. In the case of field technician, those findings will suggest to encourage those informal gathering instead of forbidding them.

In my experience, I use task analysis. I always say the essence in user modeling and task analysis is not the models or the representation but the insight coming from field study and observation.

Personas are good mean but emphasis should always be kept on field study and observation.