At this point the game is too far gone for us to hope for any meaningful improvement to the AI. Think about it for a moment. EU 4 was built upon EU 3 so the team that worked on 3 was, for the most part, carried over to 4. EU 3 has about 15 years and EU 4 9. There hasn't been anyone at the team that truly knows how all this stuff works for a long time and the game has had so many changes over the years that trying to steer the boat into another direction only leads towards disaster (see everything that happened to the AI since Emperor).
Having said all of that, the last public patch does give me hope for the future but I still think that any meaningful changes to the AI will only truly he possible in EU 5 when they get a dedicated AI guy to write a new AI from the ground up.