Having an Independent Level Control for Each Musician?

Some musicians are just naturally good at knowing what they need to hear, and some have no clue. The more you know what you want to hear, the better of a listener i think the musician is. Is it bad to be making more than one pass? What does it mean, and what can you expect if you're doing this? Do you aveany thoughts on it? N heraldo, one headphone mix or having independent level control for each musician? I prefer one mix, because i've heard people set some irrationally unbalanced mixes for themselves. Heraldo, next question.