According to fextralife, there's a time gap of 1300+ years between Origin Sin 1 and Divinity II: The Dragon Knight Saga. Original Sin 2 should be even after that. The Divine Order might be a product of Source Hunters, but chances are good that there isn't any Magister who used to be a Source Hunter from the 1st Original Sin, unless they can live for that long.
IIRC, OS2 is around 55 years before D2, though I do recall some wrangling about exactly where it is in the timeline. I think that was more with regard to whether it was before or after BD, though.