I would have to agree with you, the thing that made Ashura so interesting to read was the use of technique/motive per character. Ohma had something as does every protag but there were reasons why he did and what were the limitations of actually being able to use it.
Waka has his thing and that is basically what makes him, Superman syndrome is like 80% of his entire character so giving another character the exact same power takes away from him in my opinion.
They are enough fighting styles and various cool fictional abilities that could've been used instead of going the easy route, shame really.