Quite funny because I've just finished the "Stone of Farewell" from Tad Williams.
As far as I know, sithis & norns have a japanese style, but altered by the 'immortal' point of view somehow. The Qanuc people based on inuits is quite interesting too.

I had forgotten the Farseer Trilogy ! An I agree with you, Robin Hobb is quite good to balance the familiar and the mysterious!