Most any vendor with any sort of a sizable oolong selection will meet with mixed reviews for any given palate. I would personally even throw Teamasters and Origin into this category despite my overall appreciation for their collections (current and sadly past) as a whole.
They are not based in Taiwan, but one vendor which should not be forgotten in such discussions is Tea Urchin. Their oolong selection has some real standouts, the Alishan certainly being one.