if you're still up for another suggestion:
Normally I would suggest the EQing until the other day when I got some tracks from gainsville. The distortion was high gain and of little definition. So I realized how much I was talking my own style for granted.
I told the guy, "look man, I'm sorry but I can't work with this". I've heard the guitar and the set up live before and it sounds amazing! Mesa Triple Rectifier, Gibson Black Beauty...I mean it's top of the line stuff.
They just didn't capture it in the recording! Which is odd to me.
Sometimes there's no amount of EQing or processing that can be done to fix a unsufficiently recorded track. Lower than normal gain is a help for clarity, while high gain helps in driving the song, reinforcement if you will.
Of course you can try adding some crunch in your 2-4khz region. Sometimes I shoot for edge at 7khz. Then when that dosn't work, I try FX.
-I might sift through different variations of exciters.
-If that dosn't work, I try delays with different settings
-If that dosn't work, I try a doubler or light chorus.
-If that dosn't work, then I try to take the time to reamp the guitar through a good preamp or specific outboard unit to try and swing it in favor of the mix.
As much as I can agree that "any good engineer can work with whatever they got", I wouldn't avoid swinging things in my favor.
In other words, if you are listening to the soloed distortion tracks and they fail to stand out strong and definied (in your opinion), then you're going to have a hard mix to work with.
I think the best option is to take the sweet time of getting it to sound exactly how they want it to sound (plus a little extra exageration) on the recording, to then have strong tracks to work with in the mix stage.