Too many Stevie Ray Vaughan-abees who accept nothing less than guitar being first and foremost in the mix at all times, with solos being earsplittingly loud. I suspect that they have hearing loss in the frequency range of their guitar (or maybe across the board, who knows). I've worked with one for close to 20 years now. Excellent player, always comes prepared, but his volume is crazy.
I have spoken to the guitarist about it, but he's convinced the problem is the drummer (who is also loud), and me (though he doesn't say it to my face). I know the problem isn't me: I play in other bands, and am rarely asked to adjust my volume (when I am, it can be to turn up as well as down). Bottom line: he listens to harder rock where guitar is loudest in the mix, so that's his norm.
At least at gigs we (sometimes) have a soundman to help keep him under control, but rehearsal can be nuts. Originally, only his guitar rig was too loud. Then we acquired a lead singer who said "I'll put you through the PA so you won't have to run your guitar rig so loud". That worked OK until that lead singer retired and was replaced by a new one unwilling to rock the boat. As you all have guessed: the guitarist is now too loud in the PA as well as his guitar amp. Genie's out of the bottle, no way of taking away his PA support. I actually tried, saying "we will hear the singer better if you stay out of the PA", but no dice of course.
Sometimes I think of quitting, but they are getting fewer gigs (in part because I'm getting more from my other projects), and fortunately they don't rehearse very often (in part because I make myself less available). So I don't have to deal with him as much as I used to.
Thank you for tolerating my rant.