I've been talking about improving chatbots at the www.dtbsummit.com in London.
Here are a few ideas about it.
1. Understand and improve metrics.
2. Design good UX for business. customers (contact center staff, products, etc.)
3. Desing good UX/UI in the channels where the bot 'living in.'
4. Look beyond - create new features like widgets, voice messages, etc.