Sample applications are rarely difficult to make. I built a bot as an experiment for my team (https://m.me/PigeonCorps) and we've run into a lot of issues that fall outside of intent classification and response. The most complex issues related to non-trivial chatbots (or atypical chatbots) in my experience have been:

  - session management
  - horizontal scaling
  - dealing with platform changes
  - dealing with platform downtime/bugs
  - hierarchical data presentation
  - matching intents within hierarchical/nested flows

I agree, however, that most chatbots we see are not incredibly complicated, however, I think the typical points that are emphasized in these types of articles (intent classification) are not the hard parts.