I agree that hue rotation makes for some weird gradients. Linear RGB is an acceptable color space for gradients, because gamma correction is accounted for. But performing a linear interpolation in sRGB or the like leads to a linear gradient which appears to ramp steeply from one color stop to the next. However, if you compare Linear RGB with CIELAB then you'll notice the same thing, the CIELAB gradients look smoother as linear movement through the color space more closely mirrors linear movement through our human perceptual system.