Nidalee and Ahri are vastayan.
Vastaya are mostly from Ionia.
Karma and Varus are from Ionia.
Ionia are based on Asian culture
So what I'm seeing is rito only think you can survive competitively in esport is to be from Asia.
I don't think Ionia is very strongly based on Asian culture. Some Ionians 
appear to be European, while some Demacians 
appear to be Asian, so I think Riot has tried to avoid making any continent/nation into a symbol for a real-life race/culture/ethnicity. The real-life Ionians were Greeks, and while they did interact with Asians and there were Indo-Greeks, etc., they were still culturally European. Varus even has a Greek -us suffix on his name. I think Riot wanted to be able to use a mix of cultural inspiration for Ionia and they just picked the name because it gave a sense of "east" due to real-life Ionia being an eastern fringe of the ancient European world.
Varus is kind of hard to tell if he is european or asian base because of the demon pants thing but you do have appoint about his name. Kayn was initially noxus and with Irelia new VO Xin is confirmed to be from ionia.
Nidalee is human not Vastayan
Well, Tencent Holding IS Chinese, so it should go without saying they do favoritism.
