As for complaints that AI Dharmic religions never seem to stray out of India... IMO that depends a lot on the start date and what, if anything you are doing in the area. Last time I was playing a Zoroastrian game working to become the Saoshyant, and after beating up Habbari during a Holy War, Pratihara gobbled them up and I was fending off them as much as I was the Abbasids for much of the next century or so.
Yeah, I don't quite get that complaint either. I see Hindus push out of India all the time, with the AI sometimes reaching as far west as Persia.
One complaint I do understand is that nothing else seems to penetrate into India, partially because the Holy Orders are so strong. Thankfully, Paradox is rebalancing the Holy Orders and revising AI behavior in the JD patch.