A band will always be at the mercy of the sound guy. I've toured and played out a ton myself and its true that most sound guys suck or are just glorified Dj's. Definitely find someone you know and trust to run your sound whenever possible. Of course like others have also said most venues and headliners wont let you go near their mixing board so I recommend taking that up with the venue or whoever before agreeing to play a show. Ask if you can bring your own sound guy and if they say no then you can decide right off the bat whether you think its even worth it to play the gig. One thing's for certain though, no matter how much money you spend on gear, or practice, in the end its pretty much all up to the sound guy, especially in bigger venues which is usually the last thing bands think about before playing. When you get stuck with a shitty sound guy most of the time theres just nothing you can do and the only way is to soldier on through the set. A lot of times though the mix onstage is very different from the mix the crowd hears through the PA. For all you know you could sound great even though you cant hear yourself on stage. Always when sound checking have a friend or just ask someone to stand in front and let you know what its really sounding like. Havent tried IEM's or other personal monitoring solutions myself really cuz a piece of me really just wants to believe that maybe this time the sound guy will get it right haha. But personally I'd rather not hear myself at all and have the crowd and fans think its sounded amazing than the other way around. It may not feel as rewarding but it beats the hell of out thinking you sounded great and being told you sucked lol.