I'm also having some issues with the 2019 Supercar Rallycross AI. They always post incredibly fast times when not in the same race as the player. I find that I can consistently win the heat race by 1-2 seconds to to the nearest AI driver, but always end up in the lower half of the time-sheets in the qualifiers, even when racing some of the quicker AI drivers in the same heat. These AI drivers I have just beaten then go on to post times several seconds faster in the next heat race when they are not in the same race as the player.
This become quite frustrating when completing championships, as its very difficult to score good points in the qualifiers or even make it through to the semi finals on some tracks where the AI are particularly strong such as Mettet or Barcelona.
Also, as previous posts have mentioned, the AI have some really odd joker lap strategies. Notably, if an AI driver is leading the race on the first lap, they always take the joker effectively giving up the lead and in most cases, any chance of a good result in that race as they just get stuck in traffic.
Hoping these issues are soon fixed in a future update.