Stating channel levels is largely irrelevant here, as it all depends on your amplification.
1. How loud are the back-line amps and un-amplified drum kit
2. How loud does your FOH system go.
Having said that......I normally put everything minus vocals through a group, then with one fader movement I can have more or less instrumentation, while keeping the instrumental mix intact.
But i have done plenty of gig where there is only vocals going through the PA, or vocals plus a small boost for solos.
AND i've also seen plenty of pub/200 capacity gigs where they have tried to ram everything into an under-spec'd PA and then wondered why they cant here the vocals!
(really? you need overhead mics? when most of the audience are less than 10 meters away?!?!?!)