when i left the tint, defuse, normal alone and only modifying the spec i didn't really encountered any issues... but then again i imported the textures with the old tool soo not sure how accurate that is for other ppl...
Depending on the change u make, if u modify the diffuse (more than just a color change), and dont modify any of the other textures, it'll look wierd, since the normals will no longer line up with the details of the diffuse. But just making small modifications like increasing/decreasing spec amount, then yeah you dont need to modify all of them, for example, with my recent experiments, I only change the tint to start off with, then diffuse and spec, I didnt even touch the normals, because I was only doing color changes to the diffuse, all the details were still where they should be.
@Eham btw have u tried to make any changes to the spec map alone to weather confirm or deny if my tests were true by using ur new tool?
What were your tests? I did mess around with the spec map, but that was mainly to decrease the spec amount (By modyfing the green channel). And I modified the blue channel to make the whole thing blue to see what that would to my metal surface, seems it changed the spec a bit. Oh and I also set the red channel to all one color, but did not observe any great difference in that. I mainly just wanted a consistent spec across the whole character to view any other differences when modyfing tint.