@ianism is incorrect here.
AI in DiRT Rally 2.0 works similar to how it does in DiRT Rally:
The system is largely similar, but with additional variances based on DiRT Rally 2.0 features, like weather, tyre wear etc.
I believe @EvansR5 and @jonny174 set the Bogey Times now since they're the fastest guys we have.
AI times are not dynamically scaled based on human performance.