I've been playing around with setups etc, I feel like the problem isnt too bad in the first season of Career/My Team, it's only really noticeable once the cars get upgraded and the AI naturally get faster.
I've turned off TC completely and feel like that's also helped a little bit, also people who have made setups are starting to create setups solely for the purpose of racing the AI - shouldn't have to do this but it's a short term fix.
In no means am I saying there's no problem at all, because especially after Season 1 it makes racing the AI incredibly frustrating when it feels like they just have unlimited battery, which is probably the most likely issue rather than something inherent in their code.