I'm intrigued to know why you are using P16s to control your IEM mixes rather than the X air Q interface for the other guys? Don't get me wrong, I love the P16 as a user interface when I have had the chance to use them, but they are really expensive. I haven't been able to justify getting them to use with my XR18.
I bought one because the drummer needed a headphone amp, and it seemed like a no brainer to spend the extra money.
I bought the second because the guitarist gets in the "fog of war" when we're playing, and I wouldn't want him to accidently turn up something on FOH instead of his own mix.
Third one is a spare/waiting for a keys player.
If/when we upgrade to the X32 platform, we'll still be able to use them, so they're kinda future proof too.
Depending on how much your mix relies on hall acoustics and stage bleed, yes, highly probably. Say, a guitar is pretty loud onstage in your soundcheck. Thus, you don't put it through the PA much. When people gather at the front of the stage to form a pit (or dance), it will change how the people further back will hear it. People will most likely absorb the highs, so the mix gets bass-heavy and possible unintelligible very easy. All of this, of course, depending on how the room sounds, how many people come in, how your PA is set up, how much of your mix is from the PA etc... In a sizeable, near perfect room, this is much less of an issue.
With PA support but without mix engineer, all band members should know to not change their levels drastically during the show.
My guitarist runs direct using an AxeFX, all the patches he uses are acoustically the same volume, so I don't have to worry about this.
Why can't these guys adjust these patches so the levels are all even?? Not trying to be a jerk but our lead player's volume is all over the place during a show. The sound guy is constantly tweaking. It shouldn't be that wa, right? I mean, I understand bumping for a solo and what not. But he's incredibly inconsistent.
Fire the drummer?
Is he using alot of effects?
Not sure if you were asking me or @StraffordMike, so I will answer.
Yes, and I use a fair amount of bass and vocal effects, but we use the XR18 at practice in addition to live shows, so any volume/tone changes are noticeable and dealt with at practice.