Mary sue is a particular trope mate, not a stereotype. As for the characters YMMV. An aristocratic vampire is a trope sure, the Gith companion doesn't come across as chaotic evil to me. She comes across how I'd expect a gith warrior to come across; obsessed with their mandate and hostile to those that get in her way. The Priestess of Shar clearly has depth to her character as you get to know her a bit more. Luckily if you don't like these characters they're not the only one on the roster.
I'm aware, I'm generalizing, but I suppose "Trope" would have been more apt. The Gith most certainly strikes me as chaotic evil, from her obsession to her mandate, to her perspective that everyone and everything else is either a tool or slave to be used. I don't find our resident Priestess of Shar to be particularly deep beyond the typical "I'm a moody edgelady who worships and evil goddess and has secrets". I just find it generally disappointing that it feels like I could find each of these companion characters in a sample character section of any of the core rulebooks. It feels like they're just an afterthought, or were thrown together with the hope that nobody would notice.
