Gouken was buffed in every version of SF4 and that made no difference. In situations like those I see it as a testament to the design of the character. You have designs like Vega or Guile, who are constantly 2-3 changes away from being broken, them you have designs like Gouken where they just can't get rightIt's been so long since I played SF4 that I'm struggling to see the gouken/Manon parallels. I'm curious to hear where you're going with that.
I feel she's a few tweaks away tbh. Speed up her drive rush and give her a combo off cr mk on cc/pc. She'd instantly be way better.
I'm not the Manon guy so I tried to avoid being too declarative about her but I think she's really badly designed. I think Capcom made some ambitious design choices and they just didn't work out in her case. Her normals are somewhat unique but they also happen to be some of the worst normals I've ever seen. The medals system seems like a good idea until you realize they designed the medal system then built a character around it. They were so afraid of making the system too strong they gave her this uncohesive toolbox, which also weakens the medals system anyway
I'm not saying she can't be made better. Her having a real drive rush would be a start and Cr mk confirm would make a difference, but I think fundamentally she's just a Gouken ass bytch