Hmm... I've heard the "Hide behind distortion" thing before too but quite honestly playing with tons of distortion and treble can be quite hard because, as Andy 82 said, any quiet sound of a still ringing string is picked up and it might even be turned into feedback. If you're practicing harmonics (esp., pinch harmonics) start with distortion or your life will become too hard.
As for hitting strings damn hard, I guess that's good practice because you will find that as you speed up the notes get quieter, this makes it harder to get as much rhythm into your playing.