The real question is why do people believe Pandaren are "too soft" for Warcraft?
Pandaren have a rich and diverse ancient chinese styled culture with many dark and extreme facets. I mean have you seen some of the shit the Shado-Pan do to their enemies?
The only explanation I have been able to get from Pandaren haters is either "cus Pandas lol" or "copied kung-fu panda movie must be kiddie shit". Give me a real reason as to why Pandaren don't fit into Warcraft using existing races and story elements so I can prove you wrong.