|By Iain, via Wikimedia Commons|
Here's a case where using your ears isn't enough by itself, the context also matters. When the disappearing-distortion-solo happens, it usually is because there is too much distortion dialed in. All the new harmonics generated by distortion change your place in the EQ spectrum of the mix, you find you're competing with the frequencies being generated by the other instruments, and there's no clarity. Reaching for the volume knob doesn't help, it just makes the mud louder.
When you can't hear yourself in a band, sometimes reaching for the tone knobs is more effective than reaching for the volume knob. Recording engineers know this. If you isolate instruments in a good mix, they may sound thin or strange, yet together the sound is working. For example, the bass and bass drum live in the 45Hz-250Hz area. The other instruments can stand to lose everything below 250Hz to stay out of their way. A heavy guitar player is not going to like the sound of this by itself, but allowing the low end of the guitar to overlap the bass will just generate mud and the mix will suffer.
Last year I got a 7 band EQ pedal that I have set for a slight mid boost. If I don't think my solo is standing out enough, I've been surprised at how well this makes it cut through when I step on it--same volume, more presence.
Playing around with home multi-track recording is a great way to see this in action, and gives you full control over all the variables.