hey man
as far as I'm aware yes... that's what I do when I mix... turn it down a bit. And I never use any plugs on the master - I leave that for mastering.
In pro tools, when I select ALL the faders and knock the level down, I hear a difference in the mix... however, when I turn the master fader down a touch, that doesn't happen...
OK, so let's be a bit more objective about this... If you have a snare drum that is very snappy and it's the loudest thing in the mix, it's very likely that the peak of that snare is a lot higher (sharp transient) than the rest of the program. So if you set your mix so that the peak of that super loud snappy snare sits at -4dB, it might make no sense (snare solo album)... having that comp on the master buss is helping you to catch that transient at 0dB... So what I want to say, if this is the case (or similar) then leave things as they are and the ME will deal with it... not the best, but it's workable...
...But think about this: If you send me a mix that peaks at 0 and I want to add 2dB of top and a tad of bottom end what's going to happen? it's going to the RED.
not the end of the world, but if you want me to "enhance" your mix you should leave us some room to work.
I hope this helps (?)
Oh and BTW, in some cases I have normalised (peak) tracks down in level to get a bit of headroom to work on... not a pretty practise when you are as OCD as I am, but sometimes we just have to do things like that... crazy world.