We soundcheck in rehearsals the same way as you would mix in a recording studio. Drummer starts playing a groove at a comfortable volume, then I'll start playing some bass and adjust volume and tone to lock in with him and yet be clearly defined.
Next is the lead vocal. Remember (and this is REALLY important), the lead, whether it's vocal, solo guitar, keys, is the most important thing to be heard. And the bass and drums form the foundations. Everything else (rhythm guitars, background keys etc) fits around them. This next bit isn't a dig at the OP, but... It can be a heard lesson to learn that unless you are part of a supergroup or a solo artist, you or another band member are not the key focus of the band. If your job is backing, filling a void, providing the groove, suck it up, turn down and do that job. If you get your spotlight moments then great, take it up a notch and go for it, but there's nothing worse than a prima donna backing musician take over, whether it's bass, drums, guitar whatever. Sit back and enjoy yourself.
Then we bring the guitars in one by one, each filling a vacant area of sonic space, one has a mid centric tone, and the other a top centric.
The advantage of doing this, building things up, is you can hear when things don't sound right. If at any point you something sounds mushy, boomy or too loud, you can easily identify what the cause is and fix it.
but I am getting on a bit...) and totally agree with what you're saying. It all comes down to where you sit in the mix - too low and you're screwing with the kick / toms, too high and you're in geetard territory. And nobody wants to be a guitarist, right?
