Ideas for Dual Maining characters

Okay so I posted before that I have 12 characters, one of each class. I finally have it to where I decided to only focus on my affliction lock and my ret pally. But in terms of doing the games older content and exploring (I'm new so it's all a first time for me), I don't know how to go about this. Should I only explore the old content, farm mogs, etc on one of the two characters, do everything twice, or split it in half? Does anyone have a reccomendation? my inclination is focusing one area on one of them, and do different content on the other. I don't know why, but this is driving me crazy to think about