I demand explanation. This statement sounds retarded. Your statement is based on what examples?
Because I am 100% sure that any smart developer, before bringing out new content, tests new content. It is not like people add something completely random with random stats, skills and just watch how things would turn out.
The fact that some classes can flat out one shot/bleed you to death/and make you have no chance to attack from start to finish during a match, so there is no way to even consider anything new to this game before balancing out everything within it. Madrid is pretty probably saying a new race will make it even more unbalanced. Elsword is a perfect example of adding new classes without caring about balancing the previous, just becomes more and more broken.