Here's my view.
The overall volume must be louder than the crowd. You don't want the cheering or the chanting to be louder than the band, cuz that throws them off.
You want the guitars/bass/keys/vibrophone/accordion louder than the drummer. Drums have no volume controls. Yes, there are such things as soft-playing drummers, but not in metal! So the guitarists and bassist must be able to get loud enough to balance with their drummer. In most small clubs, that means the bass drum should really be the only thing miced to get that lovely chest thump, but that's in an ideal world without screaming drunk people.
What WOULD be nice, however, is if guitarists knew how to dial in their TONE correctly. This coming from a bass player is gonna chafe some asses, I know, but TOO BAD! Every shitty band I see or hear, the guitarist's tone sounds horrible. Why? Cuz they're playing their amps at full volume, using their bedroom practice settings. They don't take the time to listen to themselves and their gear at full stage volume and say, "Holy crap that's a lot of mud I better dial out some of that low end..." and they just turn their guitar tone to deep rumbling nothingness. No definition, no clarity, no actual discernable characteristics to their playing. Just a wall of mud.
This is why wireless systems are so lovely. When we set up, we can walk out in the crowd and listen to our amps at a distance to tell if something isn't balanced right. My brother's rig has his basement settings saved and his on-stage settings saved, and even after that he can still dial the low end to fit the stage. He starts up his rig, warms up for a minute, and listens to it in the middle of the room whenever he can.
Oh, and one more thing. There is such thing as good guitar tone that DOES NOT HURT YOUR EARS. If you need to wear earplugs because your tone is so sharp and harsh and grating, not because your band is loud, then your tone sucks and you need to FIX YO SHIT. It's quite easy to take an EQ and wiggle knobs until you find the magic frequency that is too damned painful. When you find it, take it out. A good guitar tone sounds good at max volume without needing earplugs to keep your ears from throbbing. After that, THEN put the plugs in to keep from going deaf once the whole band starts kicking.
There. That should alienate me from a ton of six-stringers here.
