Well it will be easier to Juice Sal up, when you join a room of 61's and hide in the corner for an hour. You will likely level up so often, you will spending the whole time fixing your class.
I never power level. The only time I play with any one I start a new character. I had 4 people I played with and their characters leveled up with mine. The Mechro was for solo. I dont see the guy I made the Gunzerker with a person I dont see often. I don't farm or anything, I just play through the missions over and over again. I was just seeing if any one else did the same.