Orin and Gortash have potential to be just as good I think, but they don't get opportunities to be truly seen. They have to share the spotlight with each other, those 1000 irrelevant side quests, and the brain.

Also, with Ketheric,
the game practically forces Isobel on you, you realize who she is and what happened,
you have his personal motivations for becoming the way he is. To get to know Orin and Gortash you have to put effort into finding things yourself (letter, diaries, some people) in an oversaturated city.