Sorry, I did reread and there was more information on the Majhan. My bad. :?
However, the information *as it is in the relevant parts of the RPG* don't seem to really suggest that the Majhan are, indeed, the Shianti. I'm wondering if maybe Dever's original version of them had them as independent sorcerers.
Also, I'd suggest that the Northern Shianti (Ancients/Majhan) possibly fell prey to the evil from the Darklands and Naar, accounting for their difference in temperament. Or that, possibly, the niceness of the ones in Grey Star is a result of being humbled by a goddess. Maybe at one time the Shianti *were* cosmic badasses.
Are the Suukon canon? The only place I recall hearing that name for them was in the Legends. And I can't remember what country had about them, either.