Aah yes.... the age old problem of the musician who can't hear what's coming out of his/her instrument.
I always think that if every player could step in front of their horn/axe and really hear what is going on, they'd start playing totally differently and better for it. I've had many musos in the studio who are horrified at how they sound on tape. But after a few simple tests, they realize that that is indeed how they sound.
Guitarists are usually the worst because most of them stand on top of their amps and never really hear what comes out of them. When I track a guitarist using an amp I put him at one end of the room, and his amp at the other facing him, and this is generally the first time he has ever really heard it.
It's harder for drummers because as soon as you put somebody else on the kit, it sounds different. I keep my kit set up in my studio and a variety of drummers use it. I always tune it up pretty much the same, but it sounds like a different kit on tape with each player. So drummer really need to trust the engineer.
Sorry for rambling
Mark