Unfortunately, there are many fader pushers who like to call themselves sound guys, who are as bad at what they do as there are guitar players who feel the need to "crank it to ELEVEN" to get their "tone".
As someone who does both, I can tell you its a delicate balance between letting the sound guy "do his job" and the guys on stage controlling their on-stage levels. To be sure, many FOH folks are crappy and love bass/drums and have no idea where other instruments fit in the mix. If you get one of them at a venue, you cannot win! Just do the best you can and get thru it.
One the flip side, as a sound guy, I've lost count of the number of times I've had folks (including the guitar players wife/girlfriend) come up to me at a gig and tell me they can't hear the guitar. They are usually related to that individual and think that nothing else should be heard. I don't care if you ARE Steve Vai, I'll fit you in the mix where the music warrants.
I did lose one repeat customer 'cus his wife was a PITA doing just. I'd already had to go up to the stage at LEAST 3 times in the first set and get this guy to turn down amp volume - he was SO LOUD that he was drowning out the drums !! - and his wife pitches a fit about not being able to hear him. I can assure you there was plenty guitar in the mix, jsut not enough for her !! I suggested she move closer to the stage
You can imagine how that went over.. anyway.
Point being, if you are not comfortable with the FOH mix, talk to the sound guy. Don't DEMAND. Be reasonable, 'cus for every one of you that approaches him that way, the guy has probably dealt with 20 that are *ssholes. When I'm running sound, nothing turns me off faster that a demanding musician, so I know how that guy will react.
Be nice, explain your issue and work with the guy. There may be a logical explanation. He may not have heard you before and not know the music or where the lead breaks are. Plus, many older sound guys have hearing loss, and many younger ones run sound 'cus they can't play an instrument. Most basically want to to a good job.