I lead a team that works on several hundred bots scraping at high frequency. We also separate the problem of site structure and payload parsing, though slightly differently.

We have a low frequency discovery process that delves the site to create a representative meta-data structure. This is then read by a high frequency process to create a list of URLs to fetch and parse each time.

The behaviour can then be modified and/or work divided between processes by using command line arguments that cause filtering of the meta-data.