You're right. My solo tone would already be set to a few dB higher than my rhythm tone. I guess I should have worded it better. I meant for parts where there are simply 2 rhythm guitars playing at the same time, but playing different parts and one should be a little above the other (not necessarily a lead tone volume).
But considering the looper is just a perk in this controller, and not supposed to be the main purpose, I'm very pleased with it. I'd much rather have this, than nothing at all, which is what you'd find in most controllers.