Exar Kun/Legends

How important was naga sadow to the sith after him? like for example exar kunn has a noticable affect on the sith after he dies. So does naga sadow have a similar affect?

Legends characters some how make it into canon with no story at all because one person says there name and then everyone forgets about them and they have no story? What is up with that? Take Darth Revan or Exar Kun :hope I spelled his name right: And Tenebrea and etc someone says there NAME once in Canon and now there in canon with no story AT ALL which half of that makes no SENSE take Exur what about the Rakghoul's? He made what about that? Are the Rakghoul's canon along with the Old Republic comics books, Games and etc? and they just have a little story which does not even help because then your hanging with all these other stuff that makes it sound like this also should be canon but its not? Any thoughts about this and I don't mean to come off rude or anything.

Kristen Dunst/Scarlett Johansson=Mara Jade Skywalker

Sam Witwer=Exar Kun

Sam Witwer=Galen Marek/Starkiller

Alexandra Daddario/Naomi Scott=Bastila Shan

Christian Bale=Darth Malgus

Alexandra Daddario=Satele Shan

Matthew Lewis=Jacen Solo/Darth Caedus

Mark Strong=Darth Malak

Keanu Reeves=Revan

Emma Watson=Darth Zannah

George Lucas=Valkorion

Ralph Fiennes=Darth Plagueis

Mark Strong=Darth Bane (edit)

Who would you cast?