I just found a bug in beta 15 (and 14, and 13, and 12..etc.): if you use ATTR_shiny_rat or GLOBAL_specular with an intermediate value, e.g. between 0 and 1, you get an oily effect when HDR is off.
This is a bug in one of the shaders. We didn't see it early because I have encouraged our art team to set the specular ratio to 1.0 and leave it there and use the normal map to modulate specularity. You should take that advice too! The GPU is really good at reading textures, and the CPU is not particularly good at interrupting the GPU to change what it's doing, which is what ATTR_shiny_rat does.
Beta 16 will fix this; in the mean time, what you see in HDR mode (the top two FX settings) is correct, for the purpose of figuring out if your art looks good.